March 24, 2026 • 57 mins
In this episode of Stuff to Blow Your Mind, Robert and Joe discuss the saguaro cactus of the Sonoran Desert.
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Speaker 1 (00:03):
Welcome to Stuff to Blow Your Mind production of iHeartRadio.
Speaker 2 (00:13):
Hey you welcome to Stuff to Blow Your Mind. My
name is Robert Lamb.
Speaker 3 (00:16):
And I'm Joe McCormick, and we're back with part two
in our series about the sowarrow cactus of the Sonoran Desert.
If you're not very familiar with different cactus species, but
you've seen a few old Hollywood westerns, or if you've
just I don't know, looked at picture books made for
kids or cartoons or something, you will probably recognize the
(00:37):
ciwaro as the plant icon of the American Southwest. It's
got this large, round, vertical stem, kind of like a
tree trunk, and then these limbs that branch out from
the core when the cactus is mature. We were talking
in the last episode about how the sowarro is probably
just what a lot of people think of when they
(00:58):
think cactus, despite the fact that its geographic range is
somewhat limited compared to more widely distributed species like the
prickly pair. But it's just a fundamentally very charismatic plant.
And the last time we talked about some reasons why
that might be. It's sort of human shaped, you know,
(01:19):
it's got a trunk kind of like a human maybe
with arms looking raised in a posture that's kind of friendly.
So in the last episode we talked about that. We
also just generally introduced and described the species. We talked
about the origin of its scientific name and the tie
into Andrew Carnegie. We got a bit into its evolution
(01:40):
and some interesting features like its rib structure and its spines.
And so we're back today to talk some more about
the sorrow and should we do a pronunciation note people
pronounce this word different ways. We have landed on sowarrow,
but there are other options.
Speaker 2 (01:56):
Apparently, Yeah, sowarrow is what the National Park Service says,
so we're going with that. But like you look up
souarrow in webster as, you'll find two different pronunciations for it.
So if you have one that you prefer, if you
think we're in the wrong here right in, we'll hash
it out in listener mail.
Speaker 3 (02:17):
Sure, which probably also mentioned at the top, because we
rob in the last episode you were reading from this book,
but actually in the meantime I started reading it as well,
so we're both using as a major source for these
episodes a book called The The Well I did it
there with the har g I started to Saguaro the
Sowaro Cactus, a Natural History from University of Arizona Press,
(02:41):
twenty twenty that is by a group of researchers and
scholars named David Yetman, Alberto Burquz, Kevin Holteen, and Michael Sanderson.
Speaker 2 (02:51):
Yeah. So we'll refer back to that multiple times. But
it's an easy book to pick up. It's available wherever
you get your books, and it is a great deal
more depth. So if you if you really want to
dive into the world of the Suaro, it's a it's
a great text to have.
Speaker 3 (03:07):
Now, Robert, I can't believe I didn't ask you this
in the last episode, or I hope I'm not repeating myself.
I think I didn't. We're talking about the suarrow because
you were recently in Arizona. So I assume you were
in the region of the Sonoran Desert, and so did
you get close to these things while you were out there?
Speaker 2 (03:26):
Oh? Yeah, it's like you you really can't help but
do so, Like like I said, for example, you land
in Phoenix and you leave the Sky Harbor Airport there,
you're just going to see them everywhere. And if you
do any amount of hiking within their range, which we
always try and do. Yeah, you're going to encounter them.
You're going to encounter big ones, little ones. You're going
(03:46):
to see the tiny baby suarros. You're going to see
the giants, You're going to see the ribs, the skeletons. Everything.
Speaker 3 (03:53):
Well, later in this episode, I've got some stuff I
want to talk about concerning their life cycle and abundance.
So I hope maybe you can add some uh, some
commentary from recent firsthand experience, like what ways you see
these things in their environment?
Speaker 2 (04:08):
Yeah, yeah, it'll be interesting to reflect on that because
they're you know, they're they're everywhere, so you find yourselves
as you're walking you you kind of take them for
granted at times. I mean, you can't see the forest
for the trees, right and then this this is the forest. Uh.
But then yeah, they do kind of hypnotize you as
well at times, and you you can see the human
(04:30):
form in them. You can see you know, you see
those ribs, and you start thinking of them as a
as a living thing, and so they they still cast
their spell over you even as you sort of get
used to them being there.
Speaker 3 (04:42):
Do they make sounds do they creak like trees?
Speaker 2 (04:45):
I don't remember any creaking. No, but but but maybe
I just didn't hear it. We certainly wasn't out there
in any degree of wind, as I recall. All right, well,
I want to pick up talking about the relationship between
the sorrow and rain. So summer moisture from summer rains
(05:07):
is vital to the sorrow in the form of late
summer or fall monsoon season rainfalls in the Sonoran Desert.
And we've already referenced their particular temperature requirements as well,
like they have a part of their whole range issue
is they can sustain certain amounts of freezing temperatures, but
(05:27):
only a certain amount. And it's kind of like, you know,
a few different factors what they can physically handle themselves,
and then also the sort of power ups they get
from their environment.
Speaker 3 (05:39):
Yeah, and being in the desert, you know, they're vulnerable
to temperature fluctuations on both ends, like getting roasted and
desiccated by the hot sun in hot weather and also
suffering freezes, especially in the northern part of their range,
so they have to protect against they're fighting two fronts there.
Speaker 2 (06:00):
Yeah, so their flowering period evolved to take advantage of
this particular need for summer moisture, they flower ahead of
the monsoon rains, giving plenty of time for their fruit
to develop and seeds to be distributed in time for
the deluge. Their flowers are pretty big, so eight to
ten centimeters, are three to four inches in diameter and
(06:22):
white in color. And here's where it gets really interesting.
They open at night, generally after ten pm. And remember
we're mostly talking about Arizona here, just a slim range
in California. Arizona doesn't observe daylight saving time, so that
ten pm is going to be pretty consistent as far
as clock time goes.
Speaker 3 (06:41):
Regarding the flowers, I actually read this on a USDA
National Plant Data Center sheet. It's just a fact sheet
about soorows that mention the nocturnal flowers smell like ripe melons.
Though that did make me imagine, like, wait, who's climbing
up to get up there and smell the flowers?
Speaker 2 (07:00):
Its parallels, Well, you got to do your research. You
got to get the step ladder out and smell those flowers.
Speaker 3 (07:05):
Yeah, right, so spines.
Speaker 2 (07:08):
So they open up at night? Why night, you might ask, Well, evolutionarily,
the Suarro's flower game is aimed at nocturnal pollinators in
the form of bats, such as the nectar feeding lesser
long nosed bat. I included a picture of this guy
for you here has a particular Beavis look. Yeah, I
(07:31):
think you'll find.
Speaker 3 (07:32):
I like that you included a Beavis for reference. But yeah,
it even it looks a little It's kind of blonde
like Beavis, but has the Beavis jaw and nose situation.
Speaker 2 (07:41):
Yeah, you'd think that I watched Beavis and butthead all
the time since I referenced Beavis in the last episode.
But I haven't actually watched this show in decades. But
it's a classic. It's a classic, great show. And yes,
the bat kind of looks like Beavis. And then you
also have moth pollinators such as hawk moths, so nocturnal
(08:01):
pollination is key to the evolution of their flowers. However,
while the flowers open at night, they're still visited during
the day by daytime pollinators like various bees, and this
includes indigenous bees and bees that have been introduced, migratory
white winged doves and the doves and bees in general.
(08:24):
These two daytime pollinator sources are actually the most successful
pollinators among the most northern northern of the Souaros, and
according to the authors of that University of Arizona book
that we reference, the reason for this is that most
of the far northern Saros grow beyond the range of
(08:45):
pollinating bats, and they're only able to survive it all
up there, most likely due to the bees. So they've
kind of pushed beyond the range of the pollinators they
evolve to depend upon, or at least that's the way
it's shaken out over time. But the bees are keeping
them going.
Speaker 3 (09:01):
So they have left their beloved beavis spat behind and
moved on to the bees.
Speaker 2 (09:06):
Yeah, yeah, yeah. The authors point out that the northern
Souaros likely exhibit decreased genetic diversity due to this, since
bees and doves have far more limited ranges compared to
the bats that might travel sixty miles while foraging during
their own northward migration. Now, beyond these pollinators the seedlings,
(09:28):
fruit and seeds of the suaro, which are quite small.
I don't know if we've described the seeds yet, but
they're very small. They're important for a whole host of organisms,
various ant and rodent species depend on the seeds. I
don't know if we'll get into it in this episode
or it'll be a subsequent episode, but humans, of course
make use of the fruit. We'll come back to that.
(09:50):
Termites will invade the plant to consume some of the
soft tissues, but apparently never healthy plant tissue. There's a
nineteen seventy seven study that the authors referred to here
by Steinberg and Low, and in it it was revealed
that the average sorrow produces some forty million seeds in
a lifetime. Few of these seeds. Very few of these
(10:11):
seeds will survive long enough to germinate, and of those
that do germinate, as few as one individual plant per
parent plant will survive the first year, which is pretty
pretty incredible. This despite a ninety percent germination rate given
ideal conditions. There's just that much out there looking to
eat the seeds, the fruit, or the sprout itself before
(10:33):
it gets past that one year point and one year old,
soorrows are still tiny. I encourage folks to look up
pictures of these. They If you've ever been to certain beaches,
you may have encounted sand spurs, these little little little
prickly bets with tiny spines on them. That's about what
(10:54):
a baby, a one year old sorrow looks like.
Speaker 3 (10:57):
Yeah, those things are the bane of dull being walked
near the beach.
Speaker 2 (11:01):
But yeah, they're so tiny, but yet they will become
in time and given given that the correct role of luck,
they will become giants.
Speaker 3 (11:12):
Yeah. Well, I guess that feeds right into something I
wanted to talk about, which is the is the broader
picture of how slowly Soorrows grow. And you're exactly right
that the earliest stages of growth are the most excruciatingly slow.
(11:33):
So studies carried out in Sorrow National Park indicate that
a sorrow seedling, after it germinates, on average, takes about
eight years to grow between one and one point five inches.
So you might see the seed fall leave, come back
ten years later and it's still you know, it's a
(11:53):
little little guy like that. Growth rates do accelerate after
that that early earliest decade, so it's not eight years
for every inch or inch and a half of the
cactus's height, but it still grows very slowly across its lifespan.
The Jetman at All book says that after twenty five years,
(12:14):
they are usually still less than a meter in height,
so incredibly slow growth. Depending on regional variations in climate,
it usually takes somewhere between fifty and one hundred years
for a swaro to get its first branch, the first
arm coming out wave and saying hello. Between fifty and
(12:35):
one hundred years for that, and a major factor in
the rate of growth seems to be the level of
moisture in the environment, so wetter conditions mean faster growth
and earlier branching, or at least usually mean that. The
authors of the book also note that variation in temperatures
during the winter to spring period seem to have a
(12:58):
pretty powerful effect on growth rates, with temperature volatility in
the early warm season negatively affecting growth, and I think
this is a fact they link to the idea of
increased temperature volatility coming with climate change. Obviously that puts
sorrows somewhat at risk, but even in the most favorable conditions,
(13:19):
it's probably going to be fifty years before a cactus
goes from seedling to getting an arm. The normal natural
full lifespan of the swarow is somewhere between one hundred
and fifty and two hundred years, so you know they live,
They live across multiple human generations and take multiple human
(13:40):
generations even to become the more recognizable mature shape.
Speaker 2 (13:44):
Yeah, and this is something like a number of these
details important to keep in mind later when we discuss
the indigenous indigenous mythic dimensions of the Sowara.
Speaker 3 (13:56):
So Another question is when those soarrows get to the
mature stage, you know, they're reaching the end of their
lifespan at one hundred and fifty or two hundred years
of age. How do they die? It seems older, taller
sonarrows are vulnerable to being blown over by wind and
to being struck by lightning, which happens most often during
(14:17):
summer monsoon conditions. In the colder, more northern regions of
the Sonoran Desert, old soorrows are more likely to die
from freezes during winter. And this is interesting because whereas
something like lightning strikes or wind might have a more
you know, varied you might pick out individuals in a population,
(14:38):
especially big top heavy ones, or you know, the individual
lightning strikes might take out individual soorrows in a In
the more northern regions, a local freeze can kind of
wipe out a whole crop, a whole local crop of
cactus all at once. Another interesting fact they were talking
about is that if you see a sar with a
(15:01):
branch that droops downward instead of reaching up, you know
it's got the arm turned down. This is often a
result of injury from freezing conditions in the past. So
maybe there was a freeze that didn't fully kill the cactus,
but it injured the tissues, and so now it's got
a drooping arm.
Speaker 2 (15:19):
Oh. Interesting.
Speaker 3 (15:20):
Yeah, But beyond the wind, the lightning, and the cold,
the soorrow book points out some interesting types of vulnerability
you might not expect, especially given how massive and hardy
and well defended these plants seem to be. So you
would think, you know, like nothing can hurt them. You know,
(15:40):
they got all the spines, they're huge. But the author
is right. Quote John Alcock, who monitored the same soarrows
through the year over many years time, found that a
mechanical injury as simple as constant rubbing by a palo
verdi or ironwood branch could render a soarrow susceptible to
disease and ultimate rot. So they are susceptible to especially
(16:04):
if they get abrasions on their skin. You know, something
kind of cuts into them, or hurts them, or just
kind of rubs them enough, they can get these bacterial
or fungal infections. They can get these infections that ultimately,
you know, spread through the tissue of the plant and
kill it. The authors also provide some interesting and I
(16:27):
think vivid descriptions of the death of a sorrow. To
paraphrase Hemingway, the soorrow often tends to die slowly and
then all at once. So the slowly part is that
you can get this kind of in between life and
death zombie mode cactus stage where a doomed soorrow has
(16:49):
been has been lethally injured, like it has been through
a lethal freeze, but it may continue after that to
stand upright and produce flowers, that produce flowers and fruit
for years, but it's not going to survive. It is
now doomed inevitably to die within a certain timeframe, usually
(17:10):
less than a decade. But in the time between it
keeps on living, keeps on doing reproductive activity. But in
the final stage of death this comes on with shocking speed. Quote,
what recently appeared to be a healthy plant may over
a period of a few weeks, turn yellow, then brown,
(17:30):
then brown, with black streaks, branches will collapse and fall,
and finally these sickly outer layers will slough off. And
I connected this with images of the cacti that we
talked about last time, with that peeled away skin. Look.
Speaker 2 (17:45):
Yeah, yeah, and we see the ribs inside them that
those hard woody rods that give them their structure and
their integrity.
Speaker 3 (17:56):
Yeah. And so that structure, that internal structure can help
continue to hold the cactus up even after its you know,
softer tissues and the flesh are you know, have been
critically damaged by freezes, or are infected with rod or
something like that. But eventually it all, it all falls apart.
(18:17):
Another thing that the author has mentioned. I didn't make
a note of this, but I just remembered it is
you can get a weird situation where sometimes a big
mature cactus gets knocked over, maybe it gets blown over
by wind or something, so it falls over, but it's
still sort of alive for a bit, so it falls
but continues to produce fruit and flowers.
Speaker 2 (18:36):
Oh wow, Well, I guess we see that with with
trees as well. Sometimes the tree has been knocked over
by one or fallen to one cause or another, but
it's still going to continue doing the best.
Speaker 4 (18:48):
It can't at life.
Speaker 3 (19:00):
The thing I wanted to come back to is that
before the sowaro gets to the mature reproductive stage of
its life, it has to pass through a brutal gauntlet
of survival. Rob You were talking about this in the
The Unbelievable ratio of like how many seeds are produced
versus how many actually survive to become a mature adult cactus. Again,
(19:22):
most of the info here is coming from that the
Yetna at All book. You mentioned earlier that the swaro
tends to set fruit in the early summer, and this
is usually going to be between June, mid June and
early July, and that this is timed to come right
before the summer monsoon rains. This is because the seed,
(19:45):
you know, the goal is there's a seed inside the fruit,
and the plant wants to disperse those seeds. And the
seeds are going to be dispersed either by animal transport,
so they'll be dispersed in the maybe the feces of
an animal that ate the fruit. This could be a
bat or one of many species of bird, or sometimes
it'll disperse just by falling. You know, it's not going
(20:05):
to get as far that way. But yeah, it's trying
to disperse the seeds. But when the seed hits the ground,
the seed needs warm, moist soil in order to germinate.
And the authors we're talking here about how a huge
amount of the seeds fall in places where they're just
(20:26):
not going to have a chance to germinate and survive.
Sometimes they get eaten by granivores like doves and bats,
and then they'll get pooped out on a rock surface
or inside a cave roost or some of their dark place,
or they'll get dropped in an open area that's blasted
dry by the sun, so they just don't have a chance.
Speaker 2 (20:45):
Now, I do want to add, for anyone who's not
familiar with this landscape, you do following a heavy rain,
you do have these wet areas. And I again, I
am a visitor to the Sonoran Desert. I don't regularly
spend my time there, but on my most recent trip,
we did go for a nice hike, a couple of
hikes in the Suarrows range, and it was for me
(21:09):
kind of surreal to be out. You know, it's it's
dry in so many respects. You're in the desert. You're
very concerned about how much water you have on you
And at the time I was running just a little
bit low, not dangerously low, but it was a little low.
It's like, okay, I need to get back and get
some water. But then you're also passing puddles that are
still standing. You know, you're you're you're stepping, you're walking
(21:31):
through soft earth because of the recent rain, and so yeah,
it can almost seem it can be very difficult to imagine,
I think if you haven't encountered this in this environment.
Speaker 3 (21:47):
Yeah, yeah, so there will be seasonal rains and that
we'll get more into this in a minute. But the
swarrow is very biologically poised to take maximum advantage of
when these frequent and seasonal rains do come, so that
it has water stores to tide it over through the
periods of drought. But the seedling has all these things
(22:10):
to contend with, it might get dropped in a place
that's not favorable for germination. Not to mention how rarely
in time the overall climatic conditions align for the seedlings
to germinate. The authors of the book note that quote
the necessary conditions for germination of seeds and survival of
(22:33):
seedlings seldom occur, perhaps ten times per century, often less
frequently still, so that's sort of the good case scenario
tend to. You know, it can go be a long
time in between the years when things work out just
right for the young souarros to you know, to germinate
(22:55):
and then to survive through their youngest lives. And this
leads to two very interesting consequences. One is areas with
tons of Sorrows all roughly the same size, and that's
because they're all pretty much the same age. It's like
(23:15):
a cohort or a crop that came from one of
these periods when they all grew up together, when the
conditions were right, and so you're not getting a lot
of in between because you know, there are long gaps
in between these periods when conditions are right. And it
also leads to areas that are Soorrow habitats, but at
(23:39):
certain times in history seem to have no mature soarrows,
and this latter condition can can cause and historically has
caused periods of what we might call illusory extinction. So
the authors mention this in the case of the eastern
unit of Soorrow National Park, where between the time the
(24:02):
park was established in nineteen thirty six, and some surveys
that were done in the nineteen sixties, nearly all of
the mature souarros disappeared. Quote, what was once a soorrow
forest became a comparatively uninteresting and structurally nondescript desert landscape.
Now that's alarming.
Speaker 2 (24:23):
Yeah, yeah, I believe this is the case where they
have some photographs in the book of this Yeah.
Speaker 3 (24:27):
Yeah, And some casual observers were deeply disturbed. You know,
they thought the suarros had gone extinct in the area,
but they had not. The reality was that people were
observing the effects of this reproductive pattern where the right
conditions for germination and survival of seedlings only happen on
(24:48):
the timescale of decades. Then you pair that with the
extremely slow growth of the seedlings, and you can get
periods where nearly all of the mature saros in the
region reach the end of their natural lifespan, they die,
and the younger generation of souarros are still tiny. So
it looks like the cactus has just disappeared from the landscape,
(25:10):
but it hasn't. And in fact, in the case I
just talked about the historical case with the eastern part
of Suarro National Park, there was an additional human factor involved.
Researchers figured out why this illusory extinction occurred between the
thirties and the sixties, and it was the combination of
the generational dying of a crop of mature souarros plus
(25:34):
several decades of climate being not very favorable to seedlings,
plus human behavior in the area, primarily livestock grazing, which
meant you know you're going to have cattle or whatever
live stock just tramping through the area, so that you
know that is negatively affecting the seedlings, but also people
(25:57):
cutting down woody trees for firewood or to fire kilns.
And when these human activities were eliminated, the Suaros bounced
back in the area and the cactus forest grew again.
Now here's an interesting question. Why would people cutting down
woody trees for firewood have an effect on soarrow seedling growth.
(26:20):
This is another really interesting part of the young Souarro's
survival gauntlet. So warrow seedlings need protection, and for this
protection they rely often on what are known as nurse
plants or nurse trees. So rob I wonder if this
matches with your experience of looking for the little seedlings
(26:41):
out in the desert. If you go out into the
desert and find tiny soorrow seedlings thriving, especially in the
colder parts of the Sawaro Range, the more northern parts,
it's usually the case that these seedlings are hiding under
the protective cover of a larger established plant, with the
most common species including the pallaverdi, the ironwood, creosote, mesquite,
(27:07):
and another shrub called the triangle leaf bersage or barsage.
I don't know how you say that, did you observe
this kind of thing? I've got a picture, by the way,
you can look at in the outline, rob where you've
got these young sowarrows, all kind of they're almost gathered
like children around a mesquite tree. You know, they're under
its branches and they're springing up around it.
Speaker 2 (27:28):
This is this is this is fascinating. Yeah, I didn't.
I don't think I directly observed this or at least
identified it as such. But I think part of that
is that and this is another thing that might not
be obvious to folks who haven't visited this environment, is
that you do have a lot of plant life. It's again,
we have this kind of like Looney Tunes and old
(27:50):
Western vision of like a desolate landscape with just a
few cactus columns holding up the sky. And it's not
the case. It's a it's a very very botanically diverse area.
There's so many different types of cacti as well as
as other plants that have evolved to thrive in dry conditions,
(28:12):
and so you see this multi layered effect going on,
things living and thriving in the shadow of other plants,
you know, pretty much throughout these landscapes.
Speaker 3 (28:22):
Yeah. Yeah, I was thinking, it's funny how when I
was a kid, I used to picture the desert as
essentially sand dunes like you might get in the rubolcalli
or something just like sand dunes with no plant life
except occasionally a souaro cactus poking up out of them.
And so no, the reality is something more mixed. You know.
(28:44):
You will get this actually quite crowded scrub or shrub landscape,
you know, with a lot of kind of hardy, thorny
kind of plants, and then the cactus is coming up. Yeah.
Speaker 2 (28:55):
I kind of go back to the to the the
observation that Frank Loyd Wright made that the desert was
felt like the bottom of the ocean, you know, and
like the bottom of the ocean is very diverse, but
is different compared to say a forest that one might
be used to, or you know, certainly a more temperate zone.
Speaker 3 (29:15):
So coming back to nurse plants and nurse trees, if
a soorro seed manages to reach warm, moist soil and
actually germinate, which again many do not, it first puts
out these two tiny seed leaves called coudledans, And unlike
(29:35):
the flesh of the adult cactus, which is protected by
both sharp spines and a kind of inherent nastiness and unpalatability.
Remember we talked last time about how you cannot just
cut and chug or cut and chomp the flesh of
a soorrow. It will make you sick. It's not good
for you. The flesh of the soorrow is actually tough, acidic,
(29:56):
contains irritants. It's just like not very palatable. There are
some creatures that can kind of consume it. But unlike that,
the tender cudaledans of a freshly germinated seed are relatively
easy pickings for rabbits, mice, and pack rats, ants, birds,
all kinds of things want to eat the seedlings. The
(30:18):
seedlings are also easily crushed underfoot by larger animals like
deer or grazing cattle you know, livestock animals, and they
are vulnerable to the sun, so if they don't have
adequate shade, they will get roasted and desiccated. On the
other hand, if they don't have protection against the cold,
(30:38):
they will easily freeze to death because they don't have
the mass that the adult cactuses have that helps protect
them against freezing as they don't have the mass or
the defense mechanisms of mature souarows that allow them to
survive these short dips below freezing temperatures. So the authors
of the book right quote, nurse plants are so named
(31:00):
because their shade branches litter, plus the other plants that
grow in their shade shelter the seedlings from sunburn and freezing,
protect them against trampling, conceal and shelter them from herbivores, and,
in the case of some luguminous trees, provide a nitrogen
enriched soil environment. So the nurse plant offers the whole package.
(31:24):
It keeps you from burning. Not burning keeps you from
dry you know, getting too hot, drying out and desiccating
keeps you from freezing, keeps animals from eating you or
crushing you. And sometimes it even gives you some natural fertilizer.
So it's a nice deal, right. It would almost be
nice if the soaros could find a way to pay
back their nurse plant somehow, But in this case, what
(31:47):
goes around does not come around, because it seems what
often happens is by the time the sowarrow is becoming
large enough that it has its own defenses and it
has enough mass to survive frosty weather and doesn't need
the nurse plant's protection quite so much anymore. It also,
(32:08):
at this point has a pretty robust root structure. Now
we haven't talked a lot about the root structure of
the toworro, but it tends to unlike other plants which
have a deeper taproot goes down deeper in the soil,
the soworrow tends to have a wide, shallow root structure.
And what this does is it kind of sucks up
(32:29):
a lot of the rain water that would previously have
seeped down into the soil and been absorbed by the
deeper roots of the nurse tree, and in this way,
the growing soworrow may quite often sort of murder the
plant that raised it, or if that's putting it too strong,
it at least starts to outcompete the plant that raised it.
(32:51):
Very is this the thanks I get situation? However, because
the growth of the sorrow is so slow, the author's
point out that this process never serves to wipe out
the population of nurse plants in an area because the
nurse plants have plenty of time to reproduce and recruit
new generations before they are sort of betrayed and destroyed.
Speaker 2 (33:14):
Yeah, the betrayal and destruction is still a very slow
process for the sowarro.
Speaker 3 (33:19):
Also, I mentioned that the association between soorrow seedlings and
nurse plants is stronger in the northern part of the
soarro's geographic range. The authors of the book right that
in the southern regions where you find somorrow, because of
the higher humidity in the wet season, soworrows actually don't
(33:40):
do so well under plant canopies. I think I don't
know all the reasons for this. They don't get deeply
into it. They say that they kind of suffocate under
plant canopies. I think it could be that there's, you know,
just other factors come into play, like they're more in
competition for light and stuff like that. But whatever the reason,
they don't do as well under plant canopies in the
(34:01):
southern part of their range, so instead they are found
more isolated from other plants in rocky areas, where they
rely on rocks and boulders to provide the kind of
shelter that something like palloverdi and other plants provide further north.
Speaker 2 (34:16):
Yeah, yeah, this is this is this is fascinating again.
It It may seem counterintuitive to many to think about
a cactus as being at all vulnerable to the sun,
or to think about freezing temperatures in a desert environment,
but these are all definitely in play.
Speaker 3 (34:35):
One thing I wanted to briefly come back to that
the authors mentioned, which I thought was kind of interesting,
is when they say that the cactuses are protected not
just directly by the nurse plant, but by the community
of other plants that grow up in the shelter of
the nurse plant. So it's almost like the nurse plant
(34:57):
provides a kind of an environ meant of collective defense
by you know, by by shading and protecting these plants.
A lot of the plants gathered there, and they also
kind of help shade and protect each other.
Speaker 2 (35:10):
That's a great point. And I think this is another
thing that it can seem counterintuitive to us because of
our agriculture brains. You know, we think about monocrops. We
think about, oh, there's the crop. There's a million of
them right next to each other doing well. As opposed
to the more the natural environment you'll encounter or the
approach that you'll see in like horticulture, where there's a
(35:32):
realization that no, it's not just this one plant growing there.
It's like this plant is growing next to this one,
in the shade of this one, in the partial shade
of this one, in the soil that is manipulated by
this one. You have an entire ecosystem going on there,
and it's it's more than it's more than just the individual.
(35:53):
And I guess part of that too is like humans
have an individual spirit, and we are also often prone
to think about ourselves as being disconnected from everyone else
around us in the world and the people that came
before us.
Speaker 3 (36:08):
But I think another way that it's interesting relating to
ourselves is that kind of like the relationships between humans.
You know, it's not purely it's not usually as simple
as one plant purely helps or harms the other. I
mean there it's a complex web of interactions and when
(36:28):
in which the different organisms are both helping and hurting
each other in complex ways.
Speaker 2 (36:34):
Yeah. It reminds me about our various discussions about parasites
and symbiosis and how sometimes the line between one and
the other is a little a little hard to navigate,
like when where does where does parasitism end and something
a little more even begin? Does it start as one
(36:55):
thing and become another? Yeah? It gets a little money.
Speaker 3 (37:08):
All right, are you good if we talk a bit
about metabolism. Yeah, So we've already discussed several of the
giant Sorrow's adaptations to survive in the dry conditions of
the Sonoran desert. So again, you've got things like the
fact that it uses this wide, shallow root structure to
quickly absorb massive amounts of water after fleeting rains. It
(37:30):
has this waxy epidermis and water storing tissues that allow
the cactus to hold huge amounts of extra moisture within
its flesh. And some of the authors we talked about
in the last episode compared the cactus to just an
enormous drum of water, like a giant standing drum of
what I mean, that's quite true, Like much of its
(37:51):
mass is water.
Speaker 2 (37:53):
Yeah, they're bright green, while everything other trees in the
vicinity have just turned to like brown, you know, dried out,
almost like a deathly state, and the cactus, the soarro
is still glowing green.
Speaker 3 (38:07):
Yeah, full of water, but once again, not drinkable water.
It's you know, it's trapped in some kind of mucilage
with all sorts of stuff, chemicals, and so.
Speaker 2 (38:16):
You yeah, not to drink even in survival situations, especially
in survival situations where your dehydration is not going to
be helped by nausea, vomiting and diarrhea.
Speaker 3 (38:26):
Yeah, and so there's that, but even counterintuitive things like
we talked the last time about how you might think
the spines are only to deter herbivores from eating the
flesh of the cactus, like to keep them away or
to do other things like prevent them from rubbing against it.
And you know, the spines do help with that, but
(38:46):
they also help with water and they help with controlling
the microclimate around the cactus because the spines help shade
the surface of the cactus under the hot sun, mitigating evaporation.
And they also i'll trap a boundary layer of warm,
humid air around the souarro's skin, kind of like wearing
a sweater.
Speaker 2 (39:06):
Yeah, that's crazy.
Speaker 3 (39:08):
But one interesting water conscious adaptation we haven't talked about
yet is that souarros use what's called crasulation acid metabolism
or CAAM. That's the acronym the CAAM photosynthesis. If this
sounds familiar to listeners, we did briefly talk about this
in an October episode from a few years ago where
(39:31):
we were getting into the subject of a Spanish moss
monster that was featured in an episode of cul Check
the Nightstalker. But the connection to Spanish moss is that
it also makes use of cresulation acid metabolism for roughly
the same reason as the cactus, which is to preserve moisture.
So what is CAM photosynthesis? Like other plants, the sowarro
(39:56):
gets its energy through photosynthesis, So, in simplified terms, it
uses sunlight to power a series of chemical reactions which
take carbon dioxide that it absorbs from the air through
these little holes. Most plants have these little holes on
the undersides of their leaves. In the case of the cactus,
(40:17):
it's going to be these little holes in the stem
which can open and close. These are called stomata, and
they open and close to absorb carbon dioxide from the air,
and then they fix that carbon dioxide into sugars into carbohydrates.
And so for this reaction, the plant actually does need water,
which it absorbs through its roots, and the chemical reactions
(40:40):
produce the necessary carbohydrates for the plant to live, sustain itself,
and grow and reproduce. These are the energy storing molecules.
And then the reactions also produce oxygen as a byproduct,
which is very lucky for us, lucky for all of
the oxygen breathing metazoins out there. But the most common
(41:02):
form of photosynthesis in the plant kingdom is known as
C three carbon fixation. Something like ninety percent of plants
use C three. There's another type known as C four
carbon fixation. Crasulation. Acid metabolism is an alternate form of
photosynthesis that it still does basically the same thing. You know,
(41:24):
the beginning and end is roughly the same, but it
uses a few extra steps. The CAM pathway comes with
a reduced total carbon carbon output, so it's gonna be
less productive overall for the plant. But what this pathway
sacrifices in total energy molecule production, it makes up for
(41:48):
in water preservation because it saves water. Most species of cacti,
which are adapted to hot and dry conditions use CAM photosynthesis.
So what's the trick here. I'm not going to go
into a full depth on the chemistry, but the major
macro scale distinction of camp photosynthesis is that it allows
(42:10):
the plant to keep its stomata closed during the daytime.
And remember that the stomata are these little tiny holes
or pores in the skin of the plant. Again most
often on the underside of leaves, but in the cactus
they're going to be on the outer the layer of
the stammer of the arms, and these little holes allow
(42:31):
the exchange of gas and vapor with the air outside. Now,
a C three pathway plant will keep these pores open
during the daytime so that the plant can continuously absorb
carbon dioxide from the air while the sun is shining
to power the photosynthesis in its leaves, so in the
C three pathway, it's like the raw materials are being
(42:54):
delivered to the factory while the assembly line is running.
But for the suaro in the desert environment, having the
stomata open during the day is a dicey proposition because
the sun is blazing hot, the air is very dry,
and those conditions together mean that a lot of water
inside the plant will be evaporating and escaping while the
(43:16):
windows are open. So instead, what the soarro does is
it keeps its pores closed tight during the daytime and
then opens them instead at night, when there will be
less evaporation and water losc as temperatures are lower, so
it feasts on CO two after midnight by the light
of the moon. Now, like any other plant, it still
(43:41):
needs sunlight to power photosynthesis. It can't do anything about that.
It needs to use the sun to power the reactions,
and there's none of that at night. So cam photosynthetic
plants have to convert the absorbed carbon dioxide from the
night time into an organic compound called malic acid, where
they can store it for later use. Now it's important
(44:04):
to note that malic acid is not an especially weird
or exotic compound. In fact, it is produced by I
think every plant on Earth, or if not every plant,
nearly every plant. Most plants at least maybe all of
them make this stuff. And you are already quite familiar
with malic acid. I can guarantee by taste because it
(44:27):
is the main chemical responsible for the tart flavor, and
a ton of fruits like unripe apples, grapes, pears, and plums, apricots,
all these fruits are going to have a sourness that
comes from malic acid. Now, of course, it's not the
only source of sourness in fruits. You also have citric acid,
which you get in citric fruits and stuff. But malic
(44:49):
acid is going to be the tartness in a lot
of natural fruits and some vegetables too. I think it
may be a dominant flavor in rhubarb, I think I've read.
And one in Tristing fact I came across is that
it is sometimes even used as the vinegar flavor in
salt and vinegar potato chips. Are you a salt and
vinegar guy, Rob.
Speaker 2 (45:10):
You know I'm not a huge potato chip guy, But okay,
if I potato chips are on like say, the gaming table,
and they often are I'm gonna be more drawn to
salt and vinegar than I am to whatever kind of
like spicy face melting flavor has been has been tried
it out?
Speaker 3 (45:26):
Oh yeah, the extreme flavors haberneuro death or whatever.
Speaker 2 (45:31):
Yeah, I love those things, and I support it because
that means I am less likely to eat a whole
bunch of those chips.
Speaker 3 (45:37):
Right. So, the one thing that I thought was kind
of surprising is that you would use malic acid as
a vinegar flavor in a salt and vinegar chip, because
it's supposed to be vinegar flavor, so you'd think that
would come from vinegar, which is based on acetic acid.
Speaker 2 (45:53):
I never thought. I just assumed there would be in
the factory, like some sort of like vinegar mister hitting
the potatoes slices at some point.
Speaker 3 (46:01):
So I think some chips do use the powdered form
of acetic acid on salt and vinegar chips, but other
chips use malic acid. I was reading about this in
an article for the website Serious Eats by Dan Suza
called the Science behind Salt and Vinegar Chips. This guy
went through and studied the ingredients of a bunch of
different brands of salt and vinegar potato chips, and he writes, quote, surprisingly,
(46:24):
a couple of brands in our lineup opt for citric
acid from citrus fruits, malic acid from apples, lactic acid
from milk, or even fumeric acid which apparently comes from
lichen and the quote continues to give them pucker and punch.
So I was looking through which ones are the ones
(46:45):
that opt for malic acid. Some very familiar brands like lays,
Uts and Whys all use malic acid in their flavoring mix.
So it's not the only flavor there, but it's part
of the flavoring they use for the chip. And while well,
not all tartness is exactly the same, you know you'll
get different acidic types of flavors, and malic acid is
(47:07):
going to have a slightly different kind of tartness and
acidity than acetic acid from vinegar or citric acid. So yeah,
I don't know. I guess they just try different things
and figure out what flavors they like. But sometimes you're
going to be getting malic acid in your chips.
Speaker 2 (47:22):
Fascinating.
Speaker 3 (47:24):
So again, malic acid is all over the plant Kingdom.
It's not unique to cacti, but what makes it special
in the cresulation acid metabolism plants is that they use
it to store carbon resources during the off cycle. So
the carbon from the air is stored in the plant
(47:44):
as malic acid. It's brought in during the night and
then turned into malic acid stored there, and then once
the sun fires up in the daytime, the plant can
close its pores tight to protect its horde of water
and minimize evaporation, and then vert the malic acid back
into CO two inside its tissues and then fire up
(48:06):
the photosynthetic assembly line. So rough analogy, it's kind of
like having a form of cold storage. It's a place
you can store the materials you need when it's not
convenient to be getting them at the same time you're
using them.
Speaker 2 (48:18):
And it allows the day shift to continue the night
shift's work.
Speaker 3 (48:22):
Right. So, I was looking up some other examples of
camp photosynthesis and familiar plants, especially food crops, and it
turns out it just keeps popping up in interesting places.
(48:43):
Pineapples famously actually rely on cam Another plant that uses
camphotosynthesis to survive in dry conditions is the agave plant,
the juice of which is fermented and then distilled to
produce tequila. So anytime you have a marger rita, some
of the complex sweet and tart flavors that come from
(49:05):
the tequila element. Of course margarita, you're gonna have what's
the other stuff in there? I think orange, liqueur or
something and citrus. Yeah, but the tequila part itself, Some
of these flavors are downstream products of crasulation acid metabolism.
Another cam plant is vanilla. Now this one is not
(49:25):
fully cam. I'll discuss the distinction in a minute, but
this is interesting because the orchid flower that produces vanilla
vanilla beans doesn't grow in especially dry conditions like the desert.
It tends to grow in kind of, you know, moist
forest conditions like the dense, shady understory of a humid
(49:47):
tropical forest. So if the I was wondering, if its
environment is pretty wet, why does it need cam the
answer to this question. I had a harder time finding
a very clear CLI answer to this, and I was
seeing suggestions of different reasons in different sources. So maybe
it's kind of complicated, but it seems one possible part
(50:09):
of the answer brings us back to Kulchak, the nightstalker
and paramou Fa. So remember that Spanish moss is an epiphyte,
meaning it grows not on the ground but on the
trunks and branches of trees. And because it grows on trees,
it can't put roots into the ground to collect moisture,
so it has to collect moisture from the air and
(50:30):
directly from rainfall with these epiphytic roots or with these
things I think called tricombes on its outer tissues. So
this is a less stable, less dependable way to get
water compared to having roots sunk in the ground. Thus
it needs to use cam to protect what water it's
able to suck out of the fog and out of
(50:51):
the storm. Vanilla orchids are not full epiphytes, but it
seems they are semi epiphytes, so they do they have
roots in the ground, but they climb up trees. They
climb up the trunks and branches of trees like vines,
and as they climb up they produce these secondary aerial
(51:12):
roots to absorb water directly from the air and from
the rain. So kind of like Spanish moss, the aerial
roots are a less stable, less consistent way to harvest
water than the roots sunk in the earth, and so
this could be a reason why these vanilla flowers rely
on CAM at least in part. Could be other reasons too.
(51:34):
It might have to do with light and heat stress
in their hot environments, maybe as they like climb up
trees and become exposed to the sun. But whatever the reason,
when you taste vanilla, you can think about how wow,
you know? So the compounds that I'm tasting now are
downstream of growth through in part crysulation, acid metabolism. And
(51:58):
it's worth noting that the different photosynthesis pathways are not
mutually exclusive for a plant, so many plants can switch
between like direct C three photosynthesis and CAM depending on conditions.
It seems like vanilla orchids do this. A lot of
camplants use C three when water is abundant, and then
(52:20):
they switch defensively to the CAM pathway when they are
under thread of drought. This is called facultative CAM photosynthesis.
But the swaro is an interesting exception. It is one
of the rare plants that, as far as we can tell,
basically never goes into C three mode. It is pretty
much only CAM, which is called obligate camphotosynthesis and coming
(52:44):
back to the Jetman at All book, there's this whole
interesting section about this in a chapter by one of
the authors, Kevin Halteen. Halteen writes about some experiments that
demonstrate and study the suarro's obligate relationship to CAM. One
way you can do this is you put the soworro
inside an air type plexiglass box and then measure the
(53:06):
amount of CO two in the air in the box
over time. And sure enough, these experiments show that carbon
uptake by the sowarro is almost entirely confined to the
nighttime it's after midnight. In a period between midnight and
dawn and the rest of the day, carbon uptake is
either zero or it's actually negative. So during the day
(53:29):
it's you know, releasing carbon dioxide, which we don't usually
think of plants doing. So why would that be going on?
I guess there could be multiple reasons, but Holteine explains
that this is actually pretty common for cam plants during
the day because it happens when the malic acid is
inside the tissues is converted back into carbon dioxide, so
(53:51):
the photosynthesis can happen some of this co two escapes
from you know, it leaks out of the plant before
it can be converted into sugars. And another interesting thing
that they note is that the suaro shows differential carbon
uptake across the seasons of the year, regardless of some
objective external conditions like the amount of water present. This
(54:15):
seems to be an adaptation related to the fact that
they grow more in the summer and then they shift
into a more conservative, safer gas exchange strategy in the
off season when less new tissue growth is needed.
Speaker 2 (54:29):
Fascinating, fascinating. Yeah, there's such amazing engines really, you know, again,
it's so easy, especially with such a long living, slow
growing organism as this, to just think of them as
almost inert. You know, they're almost indeed like stone columns
holding up the sky. But they are very active in
(54:52):
what they're doing is amazing.
Speaker 3 (54:53):
Yeah, and so much of it is just centered around
gathering and protecting water resources. I mean, it's to psychologize
something that's actually just biological adaptation. It's like a water obsession,
you know, it feels like almost a religious orientation toward water,
which is a metaphor actually that you know that that's
(55:15):
not new to me suggesting here. You know, people think
of that often with desert organisms having a kind of
obsessive or religious devotion to the water and their environment.
It's what everything revolves around.
Speaker 2 (55:28):
Absolutely. Yeah, Now we're gonna go ahead and close out
this episode here, but we have a lot more to
talk about with the Sorrow, so well at least do
one more episode, and in the next episode of Belief,
we're going to get into indigenous traditions that involve the soarrow.
We're going to talk about some other animal interactions and
(55:51):
some other growth features of the soaro itself, So be
sure to tune in for that episode, and in the meantime,
certainly feel free to go ahead and ride in. Any
of you desert dwellers or desert tourists out there, or
cartoon watchers and Western officionados. We'd love to hear from
you as well, if you have thoughts on anything we've
(56:12):
discussed about the souaros thus far, or any media representations
and so forth. It's all fair game. Just a reminder
to everyone out there that Stuff to Blow your Mind
is primarily a science and culture podcast, with core episodes
on Tuesdays and Thursdays. Short form episode on Wednesdays and
on Fridays, we set aside most serious concerns to just
talk about a weird film on Weird House Cinema. Yes,
(56:34):
I'm not sure if we have watched a film with
the sowaro in it. We have watched some, We've watched
desert movies. We've watched Arizona movies, but I don't know
if we've watched anything filmed specifically in the Sonoran Desert.
I'd have to go back and check, but I'm not sure.
Speaker 3 (56:50):
I was going to say, I think there's some sowarro
in the movie Tarantula, the Okads Giant Spider movie that.
Speaker 2 (56:55):
Would make sense. Yeah, yeah, number of Arizona movies. I
need to go back and check. By Yes, bright In,
We'd love to.
Speaker 3 (57:01):
Hear from you huge thanks as always to our excellent
audio producer JJ Posway. If you would like to get
in touch with us with feedback on this episode or
any other, to suggest a topic for the future, or
just to say hello, you can email us at contact
a Stuff to Blow your Mind dot com.
Speaker 1 (57:23):
Stuff to Blow Your Mind is production of iHeartRadio. For
more podcasts from My Heart Radio, visit the iHeartRadio app,
Apple podcasts, or wherever you listen to your favorite shows.
Welcome to Stuff to Blow Your Mind production of iHeartRadio.
Speaker 2 (00:13):
Hey you welcome to Stuff to Blow Your Mind. My
name is Robert Lamb.
Speaker 3 (00:16):
And I'm Joe McCormick, and we're back with part two
in our series about the sowarrow cactus of the Sonoran Desert.
If you're not very familiar with different cactus species, but
you've seen a few old Hollywood westerns, or if you've
just I don't know, looked at picture books made for
kids or cartoons or something, you will probably recognize the
(00:37):
ciwaro as the plant icon of the American Southwest. It's
got this large, round, vertical stem, kind of like a
tree trunk, and then these limbs that branch out from
the core when the cactus is mature. We were talking
in the last episode about how the sowarro is probably
just what a lot of people think of when they
(00:58):
think cactus, despite the fact that its geographic range is
somewhat limited compared to more widely distributed species like the
prickly pair. But it's just a fundamentally very charismatic plant.
And the last time we talked about some reasons why
that might be. It's sort of human shaped, you know,
(01:19):
it's got a trunk kind of like a human maybe
with arms looking raised in a posture that's kind of friendly.
So in the last episode we talked about that. We
also just generally introduced and described the species. We talked
about the origin of its scientific name and the tie
into Andrew Carnegie. We got a bit into its evolution
(01:40):
and some interesting features like its rib structure and its spines.
And so we're back today to talk some more about
the sorrow and should we do a pronunciation note people
pronounce this word different ways. We have landed on sowarrow,
but there are other options.
Speaker 2 (01:56):
Apparently, Yeah, sowarrow is what the National Park Service says,
so we're going with that. But like you look up
souarrow in webster as, you'll find two different pronunciations for it.
So if you have one that you prefer, if you
think we're in the wrong here right in, we'll hash
it out in listener mail.
Speaker 3 (02:17):
Sure, which probably also mentioned at the top, because we
rob in the last episode you were reading from this book,
but actually in the meantime I started reading it as well,
so we're both using as a major source for these
episodes a book called The The Well I did it
there with the har g I started to Saguaro the
Sowaro Cactus, a Natural History from University of Arizona Press,
(02:41):
twenty twenty that is by a group of researchers and
scholars named David Yetman, Alberto Burquz, Kevin Holteen, and Michael Sanderson.
Speaker 2 (02:51):
Yeah. So we'll refer back to that multiple times. But
it's an easy book to pick up. It's available wherever
you get your books, and it is a great deal
more depth. So if you if you really want to
dive into the world of the Suaro, it's a it's
a great text to have.
Speaker 3 (03:07):
Now, Robert, I can't believe I didn't ask you this
in the last episode, or I hope I'm not repeating myself.
I think I didn't. We're talking about the suarrow because
you were recently in Arizona. So I assume you were
in the region of the Sonoran Desert, and so did
you get close to these things while you were out there?
Speaker 2 (03:26):
Oh? Yeah, it's like you you really can't help but
do so, Like like I said, for example, you land
in Phoenix and you leave the Sky Harbor Airport there,
you're just going to see them everywhere. And if you
do any amount of hiking within their range, which we
always try and do. Yeah, you're going to encounter them.
You're going to encounter big ones, little ones. You're going
(03:46):
to see the tiny baby suarros. You're going to see
the giants, You're going to see the ribs, the skeletons. Everything.
Speaker 3 (03:53):
Well, later in this episode, I've got some stuff I
want to talk about concerning their life cycle and abundance.
So I hope maybe you can add some uh, some
commentary from recent firsthand experience, like what ways you see
these things in their environment?
Speaker 2 (04:08):
Yeah, yeah, it'll be interesting to reflect on that because
they're you know, they're they're everywhere, so you find yourselves
as you're walking you you kind of take them for
granted at times. I mean, you can't see the forest
for the trees, right and then this this is the forest. Uh.
But then yeah, they do kind of hypnotize you as
well at times, and you you can see the human
(04:30):
form in them. You can see you know, you see
those ribs, and you start thinking of them as a
as a living thing, and so they they still cast
their spell over you even as you sort of get
used to them being there.
Speaker 3 (04:42):
Do they make sounds do they creak like trees?
Speaker 2 (04:45):
I don't remember any creaking. No, but but but maybe
I just didn't hear it. We certainly wasn't out there
in any degree of wind, as I recall. All right, well,
I want to pick up talking about the relationship between
the sorrow and rain. So summer moisture from summer rains
(05:07):
is vital to the sorrow in the form of late
summer or fall monsoon season rainfalls in the Sonoran Desert.
And we've already referenced their particular temperature requirements as well,
like they have a part of their whole range issue
is they can sustain certain amounts of freezing temperatures, but
(05:27):
only a certain amount. And it's kind of like, you know,
a few different factors what they can physically handle themselves,
and then also the sort of power ups they get
from their environment.
Speaker 3 (05:39):
Yeah, and being in the desert, you know, they're vulnerable
to temperature fluctuations on both ends, like getting roasted and
desiccated by the hot sun in hot weather and also
suffering freezes, especially in the northern part of their range,
so they have to protect against they're fighting two fronts there.
Speaker 2 (06:00):
Yeah, so their flowering period evolved to take advantage of
this particular need for summer moisture, they flower ahead of
the monsoon rains, giving plenty of time for their fruit
to develop and seeds to be distributed in time for
the deluge. Their flowers are pretty big, so eight to
ten centimeters, are three to four inches in diameter and
(06:22):
white in color. And here's where it gets really interesting.
They open at night, generally after ten pm. And remember
we're mostly talking about Arizona here, just a slim range
in California. Arizona doesn't observe daylight saving time, so that
ten pm is going to be pretty consistent as far
as clock time goes.
Speaker 3 (06:41):
Regarding the flowers, I actually read this on a USDA
National Plant Data Center sheet. It's just a fact sheet
about soorows that mention the nocturnal flowers smell like ripe melons.
Though that did make me imagine, like, wait, who's climbing
up to get up there and smell the flowers?
Speaker 2 (07:00):
Its parallels, Well, you got to do your research. You
got to get the step ladder out and smell those flowers.
Speaker 3 (07:05):
Yeah, right, so spines.
Speaker 2 (07:08):
So they open up at night? Why night, you might ask, Well, evolutionarily,
the Suarro's flower game is aimed at nocturnal pollinators in
the form of bats, such as the nectar feeding lesser
long nosed bat. I included a picture of this guy
for you here has a particular Beavis look. Yeah, I
(07:31):
think you'll find.
Speaker 3 (07:32):
I like that you included a Beavis for reference. But yeah,
it even it looks a little It's kind of blonde
like Beavis, but has the Beavis jaw and nose situation.
Speaker 2 (07:41):
Yeah, you'd think that I watched Beavis and butthead all
the time since I referenced Beavis in the last episode.
But I haven't actually watched this show in decades. But
it's a classic. It's a classic, great show. And yes,
the bat kind of looks like Beavis. And then you
also have moth pollinators such as hawk moths, so nocturnal
(08:01):
pollination is key to the evolution of their flowers. However,
while the flowers open at night, they're still visited during
the day by daytime pollinators like various bees, and this
includes indigenous bees and bees that have been introduced, migratory
white winged doves and the doves and bees in general.
(08:24):
These two daytime pollinator sources are actually the most successful
pollinators among the most northern northern of the Souaros, and
according to the authors of that University of Arizona book
that we reference, the reason for this is that most
of the far northern Saros grow beyond the range of
(08:45):
pollinating bats, and they're only able to survive it all
up there, most likely due to the bees. So they've
kind of pushed beyond the range of the pollinators they
evolve to depend upon, or at least that's the way
it's shaken out over time. But the bees are keeping
them going.
Speaker 3 (09:01):
So they have left their beloved beavis spat behind and
moved on to the bees.
Speaker 2 (09:06):
Yeah, yeah, yeah. The authors point out that the northern
Souaros likely exhibit decreased genetic diversity due to this, since
bees and doves have far more limited ranges compared to
the bats that might travel sixty miles while foraging during
their own northward migration. Now, beyond these pollinators the seedlings,
(09:28):
fruit and seeds of the suaro, which are quite small.
I don't know if we've described the seeds yet, but
they're very small. They're important for a whole host of organisms,
various ant and rodent species depend on the seeds. I
don't know if we'll get into it in this episode
or it'll be a subsequent episode, but humans, of course
make use of the fruit. We'll come back to that.
(09:50):
Termites will invade the plant to consume some of the
soft tissues, but apparently never healthy plant tissue. There's a
nineteen seventy seven study that the authors referred to here
by Steinberg and Low, and in it it was revealed
that the average sorrow produces some forty million seeds in
a lifetime. Few of these seeds. Very few of these
(10:11):
seeds will survive long enough to germinate, and of those
that do germinate, as few as one individual plant per
parent plant will survive the first year, which is pretty
pretty incredible. This despite a ninety percent germination rate given
ideal conditions. There's just that much out there looking to
eat the seeds, the fruit, or the sprout itself before
(10:33):
it gets past that one year point and one year old,
soorrows are still tiny. I encourage folks to look up
pictures of these. They If you've ever been to certain beaches,
you may have encounted sand spurs, these little little little
prickly bets with tiny spines on them. That's about what
(10:54):
a baby, a one year old sorrow looks like.
Speaker 3 (10:57):
Yeah, those things are the bane of dull being walked
near the beach.
Speaker 2 (11:01):
But yeah, they're so tiny, but yet they will become
in time and given given that the correct role of luck,
they will become giants.
Speaker 3 (11:12):
Yeah. Well, I guess that feeds right into something I
wanted to talk about, which is the is the broader
picture of how slowly Soorrows grow. And you're exactly right
that the earliest stages of growth are the most excruciatingly slow.
(11:33):
So studies carried out in Sorrow National Park indicate that
a sorrow seedling, after it germinates, on average, takes about
eight years to grow between one and one point five inches.
So you might see the seed fall leave, come back
ten years later and it's still you know, it's a
(11:53):
little little guy like that. Growth rates do accelerate after
that that early earliest decade, so it's not eight years
for every inch or inch and a half of the
cactus's height, but it still grows very slowly across its lifespan.
The Jetman at All book says that after twenty five years,
(12:14):
they are usually still less than a meter in height,
so incredibly slow growth. Depending on regional variations in climate,
it usually takes somewhere between fifty and one hundred years
for a swaro to get its first branch, the first
arm coming out wave and saying hello. Between fifty and
(12:35):
one hundred years for that, and a major factor in
the rate of growth seems to be the level of
moisture in the environment, so wetter conditions mean faster growth
and earlier branching, or at least usually mean that. The
authors of the book also note that variation in temperatures
during the winter to spring period seem to have a
(12:58):
pretty powerful effect on growth rates, with temperature volatility in
the early warm season negatively affecting growth, and I think
this is a fact they link to the idea of
increased temperature volatility coming with climate change. Obviously that puts
sorrows somewhat at risk, but even in the most favorable conditions,
(13:19):
it's probably going to be fifty years before a cactus
goes from seedling to getting an arm. The normal natural
full lifespan of the swarow is somewhere between one hundred
and fifty and two hundred years, so you know they live,
They live across multiple human generations and take multiple human
(13:40):
generations even to become the more recognizable mature shape.
Speaker 2 (13:44):
Yeah, and this is something like a number of these
details important to keep in mind later when we discuss
the indigenous indigenous mythic dimensions of the Sowara.
Speaker 3 (13:56):
So Another question is when those soarrows get to the
mature stage, you know, they're reaching the end of their
lifespan at one hundred and fifty or two hundred years
of age. How do they die? It seems older, taller
sonarrows are vulnerable to being blown over by wind and
to being struck by lightning, which happens most often during
(14:17):
summer monsoon conditions. In the colder, more northern regions of
the Sonoran Desert, old soorrows are more likely to die
from freezes during winter. And this is interesting because whereas
something like lightning strikes or wind might have a more
you know, varied you might pick out individuals in a population,
(14:38):
especially big top heavy ones, or you know, the individual
lightning strikes might take out individual soorrows in a In
the more northern regions, a local freeze can kind of
wipe out a whole crop, a whole local crop of
cactus all at once. Another interesting fact they were talking
about is that if you see a sar with a
(15:01):
branch that droops downward instead of reaching up, you know
it's got the arm turned down. This is often a
result of injury from freezing conditions in the past. So
maybe there was a freeze that didn't fully kill the cactus,
but it injured the tissues, and so now it's got
a drooping arm.
Speaker 2 (15:19):
Oh. Interesting.
Speaker 3 (15:20):
Yeah, But beyond the wind, the lightning, and the cold,
the soorrow book points out some interesting types of vulnerability
you might not expect, especially given how massive and hardy
and well defended these plants seem to be. So you
would think, you know, like nothing can hurt them. You know,
(15:40):
they got all the spines, they're huge. But the author
is right. Quote John Alcock, who monitored the same soarrows
through the year over many years time, found that a
mechanical injury as simple as constant rubbing by a palo
verdi or ironwood branch could render a soarrow susceptible to
disease and ultimate rot. So they are susceptible to especially
(16:04):
if they get abrasions on their skin. You know, something
kind of cuts into them, or hurts them, or just
kind of rubs them enough, they can get these bacterial
or fungal infections. They can get these infections that ultimately,
you know, spread through the tissue of the plant and
kill it. The authors also provide some interesting and I
(16:27):
think vivid descriptions of the death of a sorrow. To
paraphrase Hemingway, the soorrow often tends to die slowly and
then all at once. So the slowly part is that
you can get this kind of in between life and
death zombie mode cactus stage where a doomed soorrow has
(16:49):
been has been lethally injured, like it has been through
a lethal freeze, but it may continue after that to
stand upright and produce flowers, that produce flowers and fruit
for years, but it's not going to survive. It is
now doomed inevitably to die within a certain timeframe, usually
(17:10):
less than a decade. But in the time between it
keeps on living, keeps on doing reproductive activity. But in
the final stage of death this comes on with shocking speed. Quote,
what recently appeared to be a healthy plant may over
a period of a few weeks, turn yellow, then brown,
(17:30):
then brown, with black streaks, branches will collapse and fall,
and finally these sickly outer layers will slough off. And
I connected this with images of the cacti that we
talked about last time, with that peeled away skin. Look.
Speaker 2 (17:45):
Yeah, yeah, and we see the ribs inside them that
those hard woody rods that give them their structure and
their integrity.
Speaker 3 (17:56):
Yeah. And so that structure, that internal structure can help
continue to hold the cactus up even after its you know,
softer tissues and the flesh are you know, have been
critically damaged by freezes, or are infected with rod or
something like that. But eventually it all, it all falls apart.
(18:17):
Another thing that the author has mentioned. I didn't make
a note of this, but I just remembered it is
you can get a weird situation where sometimes a big
mature cactus gets knocked over, maybe it gets blown over
by wind or something, so it falls over, but it's
still sort of alive for a bit, so it falls
but continues to produce fruit and flowers.
Speaker 2 (18:36):
Oh wow, Well, I guess we see that with with
trees as well. Sometimes the tree has been knocked over
by one or fallen to one cause or another, but
it's still going to continue doing the best.
Speaker 4 (18:48):
It can't at life.
Speaker 3 (19:00):
The thing I wanted to come back to is that
before the sowaro gets to the mature reproductive stage of
its life, it has to pass through a brutal gauntlet
of survival. Rob You were talking about this in the
The Unbelievable ratio of like how many seeds are produced
versus how many actually survive to become a mature adult cactus. Again,
(19:22):
most of the info here is coming from that the
Yetna at All book. You mentioned earlier that the swaro
tends to set fruit in the early summer, and this
is usually going to be between June, mid June and
early July, and that this is timed to come right
before the summer monsoon rains. This is because the seed,
(19:45):
you know, the goal is there's a seed inside the fruit,
and the plant wants to disperse those seeds. And the
seeds are going to be dispersed either by animal transport,
so they'll be dispersed in the maybe the feces of
an animal that ate the fruit. This could be a
bat or one of many species of bird, or sometimes
it'll disperse just by falling. You know, it's not going
(20:05):
to get as far that way. But yeah, it's trying
to disperse the seeds. But when the seed hits the ground,
the seed needs warm, moist soil in order to germinate.
And the authors we're talking here about how a huge
amount of the seeds fall in places where they're just
(20:26):
not going to have a chance to germinate and survive.
Sometimes they get eaten by granivores like doves and bats,
and then they'll get pooped out on a rock surface
or inside a cave roost or some of their dark place,
or they'll get dropped in an open area that's blasted
dry by the sun, so they just don't have a chance.
Speaker 2 (20:45):
Now, I do want to add, for anyone who's not
familiar with this landscape, you do following a heavy rain,
you do have these wet areas. And I again, I
am a visitor to the Sonoran Desert. I don't regularly
spend my time there, but on my most recent trip,
we did go for a nice hike, a couple of
hikes in the Suarrows range, and it was for me
(21:09):
kind of surreal to be out. You know, it's it's
dry in so many respects. You're in the desert. You're
very concerned about how much water you have on you
And at the time I was running just a little
bit low, not dangerously low, but it was a little low.
It's like, okay, I need to get back and get
some water. But then you're also passing puddles that are
still standing. You know, you're you're you're stepping, you're walking
(21:31):
through soft earth because of the recent rain, and so yeah,
it can almost seem it can be very difficult to imagine,
I think if you haven't encountered this in this environment.
Speaker 3 (21:47):
Yeah, yeah, so there will be seasonal rains and that
we'll get more into this in a minute. But the
swarrow is very biologically poised to take maximum advantage of
when these frequent and seasonal rains do come, so that
it has water stores to tide it over through the
periods of drought. But the seedling has all these things
(22:10):
to contend with, it might get dropped in a place
that's not favorable for germination. Not to mention how rarely
in time the overall climatic conditions align for the seedlings
to germinate. The authors of the book note that quote
the necessary conditions for germination of seeds and survival of
(22:33):
seedlings seldom occur, perhaps ten times per century, often less
frequently still, so that's sort of the good case scenario
tend to. You know, it can go be a long
time in between the years when things work out just
right for the young souarros to you know, to germinate
(22:55):
and then to survive through their youngest lives. And this
leads to two very interesting consequences. One is areas with
tons of Sorrows all roughly the same size, and that's
because they're all pretty much the same age. It's like
(23:15):
a cohort or a crop that came from one of
these periods when they all grew up together, when the
conditions were right, and so you're not getting a lot
of in between because you know, there are long gaps
in between these periods when conditions are right. And it
also leads to areas that are Soorrow habitats, but at
(23:39):
certain times in history seem to have no mature soarrows,
and this latter condition can can cause and historically has
caused periods of what we might call illusory extinction. So
the authors mention this in the case of the eastern
unit of Soorrow National Park, where between the time the
(24:02):
park was established in nineteen thirty six, and some surveys
that were done in the nineteen sixties, nearly all of
the mature souarros disappeared. Quote, what was once a soorrow
forest became a comparatively uninteresting and structurally nondescript desert landscape.
Now that's alarming.
Speaker 2 (24:23):
Yeah, yeah, I believe this is the case where they
have some photographs in the book of this Yeah.
Speaker 3 (24:27):
Yeah, And some casual observers were deeply disturbed. You know,
they thought the suarros had gone extinct in the area,
but they had not. The reality was that people were
observing the effects of this reproductive pattern where the right
conditions for germination and survival of seedlings only happen on
(24:48):
the timescale of decades. Then you pair that with the
extremely slow growth of the seedlings, and you can get
periods where nearly all of the mature saros in the
region reach the end of their natural lifespan, they die,
and the younger generation of souarros are still tiny. So
it looks like the cactus has just disappeared from the landscape,
(25:10):
but it hasn't. And in fact, in the case I
just talked about the historical case with the eastern part
of Suarro National Park, there was an additional human factor involved.
Researchers figured out why this illusory extinction occurred between the
thirties and the sixties, and it was the combination of
the generational dying of a crop of mature souarros plus
(25:34):
several decades of climate being not very favorable to seedlings,
plus human behavior in the area, primarily livestock grazing, which
meant you know you're going to have cattle or whatever
live stock just tramping through the area, so that you
know that is negatively affecting the seedlings, but also people
(25:57):
cutting down woody trees for firewood or to fire kilns.
And when these human activities were eliminated, the Suaros bounced
back in the area and the cactus forest grew again.
Now here's an interesting question. Why would people cutting down
woody trees for firewood have an effect on soarrow seedling growth.
(26:20):
This is another really interesting part of the young Souarro's
survival gauntlet. So warrow seedlings need protection, and for this
protection they rely often on what are known as nurse
plants or nurse trees. So rob I wonder if this
matches with your experience of looking for the little seedlings
(26:41):
out in the desert. If you go out into the
desert and find tiny soorrow seedlings thriving, especially in the
colder parts of the Sawaro Range, the more northern parts,
it's usually the case that these seedlings are hiding under
the protective cover of a larger established plant, with the
most common species including the pallaverdi, the ironwood, creosote, mesquite,
(27:07):
and another shrub called the triangle leaf bersage or barsage.
I don't know how you say that, did you observe
this kind of thing? I've got a picture, by the way,
you can look at in the outline, rob where you've
got these young sowarrows, all kind of they're almost gathered
like children around a mesquite tree. You know, they're under
its branches and they're springing up around it.
Speaker 2 (27:28):
This is this is this is fascinating. Yeah, I didn't.
I don't think I directly observed this or at least
identified it as such. But I think part of that
is that and this is another thing that might not
be obvious to folks who haven't visited this environment, is
that you do have a lot of plant life. It's again,
we have this kind of like Looney Tunes and old
(27:50):
Western vision of like a desolate landscape with just a
few cactus columns holding up the sky. And it's not
the case. It's a it's a very very botanically diverse area.
There's so many different types of cacti as well as
as other plants that have evolved to thrive in dry conditions,
(28:12):
and so you see this multi layered effect going on,
things living and thriving in the shadow of other plants,
you know, pretty much throughout these landscapes.
Speaker 3 (28:22):
Yeah. Yeah, I was thinking, it's funny how when I
was a kid, I used to picture the desert as
essentially sand dunes like you might get in the rubolcalli
or something just like sand dunes with no plant life
except occasionally a souaro cactus poking up out of them.
And so no, the reality is something more mixed. You know.
(28:44):
You will get this actually quite crowded scrub or shrub landscape,
you know, with a lot of kind of hardy, thorny
kind of plants, and then the cactus is coming up. Yeah.
Speaker 2 (28:55):
I kind of go back to the to the the
observation that Frank Loyd Wright made that the desert was
felt like the bottom of the ocean, you know, and
like the bottom of the ocean is very diverse, but
is different compared to say a forest that one might
be used to, or you know, certainly a more temperate zone.
Speaker 3 (29:15):
So coming back to nurse plants and nurse trees, if
a soorro seed manages to reach warm, moist soil and
actually germinate, which again many do not, it first puts
out these two tiny seed leaves called coudledans, And unlike
(29:35):
the flesh of the adult cactus, which is protected by
both sharp spines and a kind of inherent nastiness and unpalatability.
Remember we talked last time about how you cannot just
cut and chug or cut and chomp the flesh of
a soorrow. It will make you sick. It's not good
for you. The flesh of the soorrow is actually tough, acidic,
(29:56):
contains irritants. It's just like not very palatable. There are
some creatures that can kind of consume it. But unlike that,
the tender cudaledans of a freshly germinated seed are relatively
easy pickings for rabbits, mice, and pack rats, ants, birds,
all kinds of things want to eat the seedlings. The
(30:18):
seedlings are also easily crushed underfoot by larger animals like
deer or grazing cattle you know, livestock animals, and they
are vulnerable to the sun, so if they don't have
adequate shade, they will get roasted and desiccated. On the
other hand, if they don't have protection against the cold,
(30:38):
they will easily freeze to death because they don't have
the mass that the adult cactuses have that helps protect
them against freezing as they don't have the mass or
the defense mechanisms of mature souarows that allow them to
survive these short dips below freezing temperatures. So the authors
of the book right quote, nurse plants are so named
(31:00):
because their shade branches litter, plus the other plants that
grow in their shade shelter the seedlings from sunburn and freezing,
protect them against trampling, conceal and shelter them from herbivores, and,
in the case of some luguminous trees, provide a nitrogen
enriched soil environment. So the nurse plant offers the whole package.
(31:24):
It keeps you from burning. Not burning keeps you from
dry you know, getting too hot, drying out and desiccating
keeps you from freezing, keeps animals from eating you or
crushing you. And sometimes it even gives you some natural fertilizer.
So it's a nice deal, right. It would almost be
nice if the soaros could find a way to pay
back their nurse plant somehow, But in this case, what
(31:47):
goes around does not come around, because it seems what
often happens is by the time the sowarrow is becoming
large enough that it has its own defenses and it
has enough mass to survive frosty weather and doesn't need
the nurse plant's protection quite so much anymore. It also,
(32:08):
at this point has a pretty robust root structure. Now
we haven't talked a lot about the root structure of
the toworro, but it tends to unlike other plants which
have a deeper taproot goes down deeper in the soil,
the soworrow tends to have a wide, shallow root structure.
And what this does is it kind of sucks up
(32:29):
a lot of the rain water that would previously have
seeped down into the soil and been absorbed by the
deeper roots of the nurse tree, and in this way,
the growing soworrow may quite often sort of murder the
plant that raised it, or if that's putting it too strong,
it at least starts to outcompete the plant that raised it.
(32:51):
Very is this the thanks I get situation? However, because
the growth of the sorrow is so slow, the author's
point out that this process never serves to wipe out
the population of nurse plants in an area because the
nurse plants have plenty of time to reproduce and recruit
new generations before they are sort of betrayed and destroyed.
Speaker 2 (33:14):
Yeah, the betrayal and destruction is still a very slow
process for the sowarro.
Speaker 3 (33:19):
Also, I mentioned that the association between soorrow seedlings and
nurse plants is stronger in the northern part of the
soarro's geographic range. The authors of the book right that
in the southern regions where you find somorrow, because of
the higher humidity in the wet season, soworrows actually don't
(33:40):
do so well under plant canopies. I think I don't
know all the reasons for this. They don't get deeply
into it. They say that they kind of suffocate under
plant canopies. I think it could be that there's, you know,
just other factors come into play, like they're more in
competition for light and stuff like that. But whatever the reason,
they don't do as well under plant canopies in the
(34:01):
southern part of their range, so instead they are found
more isolated from other plants in rocky areas, where they
rely on rocks and boulders to provide the kind of
shelter that something like palloverdi and other plants provide further north.
Speaker 2 (34:16):
Yeah, yeah, this is this is this is fascinating again.
It It may seem counterintuitive to many to think about
a cactus as being at all vulnerable to the sun,
or to think about freezing temperatures in a desert environment,
but these are all definitely in play.
Speaker 3 (34:35):
One thing I wanted to briefly come back to that
the authors mentioned, which I thought was kind of interesting,
is when they say that the cactuses are protected not
just directly by the nurse plant, but by the community
of other plants that grow up in the shelter of
the nurse plant. So it's almost like the nurse plant
(34:57):
provides a kind of an environ meant of collective defense
by you know, by by shading and protecting these plants.
A lot of the plants gathered there, and they also
kind of help shade and protect each other.
Speaker 2 (35:10):
That's a great point. And I think this is another
thing that it can seem counterintuitive to us because of
our agriculture brains. You know, we think about monocrops. We
think about, oh, there's the crop. There's a million of
them right next to each other doing well. As opposed
to the more the natural environment you'll encounter or the
approach that you'll see in like horticulture, where there's a
(35:32):
realization that no, it's not just this one plant growing there.
It's like this plant is growing next to this one,
in the shade of this one, in the partial shade
of this one, in the soil that is manipulated by
this one. You have an entire ecosystem going on there,
and it's it's more than it's more than just the individual.
(35:53):
And I guess part of that too is like humans
have an individual spirit, and we are also often prone
to think about ourselves as being disconnected from everyone else
around us in the world and the people that came
before us.
Speaker 3 (36:08):
But I think another way that it's interesting relating to
ourselves is that kind of like the relationships between humans.
You know, it's not purely it's not usually as simple
as one plant purely helps or harms the other. I
mean there it's a complex web of interactions and when
(36:28):
in which the different organisms are both helping and hurting
each other in complex ways.
Speaker 2 (36:34):
Yeah. It reminds me about our various discussions about parasites
and symbiosis and how sometimes the line between one and
the other is a little a little hard to navigate,
like when where does where does parasitism end and something
a little more even begin? Does it start as one
(36:55):
thing and become another? Yeah? It gets a little money.
Speaker 3 (37:08):
All right, are you good if we talk a bit
about metabolism. Yeah, So we've already discussed several of the
giant Sorrow's adaptations to survive in the dry conditions of
the Sonoran desert. So again, you've got things like the
fact that it uses this wide, shallow root structure to
quickly absorb massive amounts of water after fleeting rains. It
(37:30):
has this waxy epidermis and water storing tissues that allow
the cactus to hold huge amounts of extra moisture within
its flesh. And some of the authors we talked about
in the last episode compared the cactus to just an
enormous drum of water, like a giant standing drum of
what I mean, that's quite true, Like much of its
(37:51):
mass is water.
Speaker 2 (37:53):
Yeah, they're bright green, while everything other trees in the
vicinity have just turned to like brown, you know, dried out,
almost like a deathly state, and the cactus, the soarro
is still glowing green.
Speaker 3 (38:07):
Yeah, full of water, but once again, not drinkable water.
It's you know, it's trapped in some kind of mucilage
with all sorts of stuff, chemicals, and so.
Speaker 2 (38:16):
You yeah, not to drink even in survival situations, especially
in survival situations where your dehydration is not going to
be helped by nausea, vomiting and diarrhea.
Speaker 3 (38:26):
Yeah, and so there's that, but even counterintuitive things like
we talked the last time about how you might think
the spines are only to deter herbivores from eating the
flesh of the cactus, like to keep them away or
to do other things like prevent them from rubbing against it.
And you know, the spines do help with that, but
(38:46):
they also help with water and they help with controlling
the microclimate around the cactus because the spines help shade
the surface of the cactus under the hot sun, mitigating evaporation.
And they also i'll trap a boundary layer of warm,
humid air around the souarro's skin, kind of like wearing
a sweater.
Speaker 2 (39:06):
Yeah, that's crazy.
Speaker 3 (39:08):
But one interesting water conscious adaptation we haven't talked about
yet is that souarros use what's called crasulation acid metabolism
or CAAM. That's the acronym the CAAM photosynthesis. If this
sounds familiar to listeners, we did briefly talk about this
in an October episode from a few years ago where
(39:31):
we were getting into the subject of a Spanish moss
monster that was featured in an episode of cul Check
the Nightstalker. But the connection to Spanish moss is that
it also makes use of cresulation acid metabolism for roughly
the same reason as the cactus, which is to preserve moisture.
So what is CAM photosynthesis? Like other plants, the sowarro
(39:56):
gets its energy through photosynthesis, So, in simplified terms, it
uses sunlight to power a series of chemical reactions which
take carbon dioxide that it absorbs from the air through
these little holes. Most plants have these little holes on
the undersides of their leaves. In the case of the cactus,
(40:17):
it's going to be these little holes in the stem
which can open and close. These are called stomata, and
they open and close to absorb carbon dioxide from the air,
and then they fix that carbon dioxide into sugars into carbohydrates.
And so for this reaction, the plant actually does need water,
which it absorbs through its roots, and the chemical reactions
(40:40):
produce the necessary carbohydrates for the plant to live, sustain itself,
and grow and reproduce. These are the energy storing molecules.
And then the reactions also produce oxygen as a byproduct,
which is very lucky for us, lucky for all of
the oxygen breathing metazoins out there. But the most common
(41:02):
form of photosynthesis in the plant kingdom is known as
C three carbon fixation. Something like ninety percent of plants
use C three. There's another type known as C four
carbon fixation. Crasulation. Acid metabolism is an alternate form of
photosynthesis that it still does basically the same thing. You know,
(41:24):
the beginning and end is roughly the same, but it
uses a few extra steps. The CAM pathway comes with
a reduced total carbon carbon output, so it's gonna be
less productive overall for the plant. But what this pathway
sacrifices in total energy molecule production, it makes up for
(41:48):
in water preservation because it saves water. Most species of cacti,
which are adapted to hot and dry conditions use CAM photosynthesis.
So what's the trick here. I'm not going to go
into a full depth on the chemistry, but the major
macro scale distinction of camp photosynthesis is that it allows
(42:10):
the plant to keep its stomata closed during the daytime.
And remember that the stomata are these little tiny holes
or pores in the skin of the plant. Again most
often on the underside of leaves, but in the cactus
they're going to be on the outer the layer of
the stammer of the arms, and these little holes allow
(42:31):
the exchange of gas and vapor with the air outside. Now,
a C three pathway plant will keep these pores open
during the daytime so that the plant can continuously absorb
carbon dioxide from the air while the sun is shining
to power the photosynthesis in its leaves, so in the
C three pathway, it's like the raw materials are being
(42:54):
delivered to the factory while the assembly line is running.
But for the suaro in the desert environment, having the
stomata open during the day is a dicey proposition because
the sun is blazing hot, the air is very dry,
and those conditions together mean that a lot of water
inside the plant will be evaporating and escaping while the
(43:16):
windows are open. So instead, what the soarro does is
it keeps its pores closed tight during the daytime and
then opens them instead at night, when there will be
less evaporation and water losc as temperatures are lower, so
it feasts on CO two after midnight by the light
of the moon. Now, like any other plant, it still
(43:41):
needs sunlight to power photosynthesis. It can't do anything about that.
It needs to use the sun to power the reactions,
and there's none of that at night. So cam photosynthetic
plants have to convert the absorbed carbon dioxide from the
night time into an organic compound called malic acid, where
they can store it for later use. Now it's important
(44:04):
to note that malic acid is not an especially weird
or exotic compound. In fact, it is produced by I
think every plant on Earth, or if not every plant,
nearly every plant. Most plants at least maybe all of
them make this stuff. And you are already quite familiar
with malic acid. I can guarantee by taste because it
(44:27):
is the main chemical responsible for the tart flavor, and
a ton of fruits like unripe apples, grapes, pears, and plums, apricots,
all these fruits are going to have a sourness that
comes from malic acid. Now, of course, it's not the
only source of sourness in fruits. You also have citric acid,
which you get in citric fruits and stuff. But malic
(44:49):
acid is going to be the tartness in a lot
of natural fruits and some vegetables too. I think it
may be a dominant flavor in rhubarb, I think I've read.
And one in Tristing fact I came across is that
it is sometimes even used as the vinegar flavor in
salt and vinegar potato chips. Are you a salt and
vinegar guy, Rob.
Speaker 2 (45:10):
You know I'm not a huge potato chip guy, But okay,
if I potato chips are on like say, the gaming table,
and they often are I'm gonna be more drawn to
salt and vinegar than I am to whatever kind of
like spicy face melting flavor has been has been tried
it out?
Speaker 3 (45:26):
Oh yeah, the extreme flavors haberneuro death or whatever.
Speaker 2 (45:31):
Yeah, I love those things, and I support it because
that means I am less likely to eat a whole
bunch of those chips.
Speaker 3 (45:37):
Right. So, the one thing that I thought was kind
of surprising is that you would use malic acid as
a vinegar flavor in a salt and vinegar chip, because
it's supposed to be vinegar flavor, so you'd think that
would come from vinegar, which is based on acetic acid.
Speaker 2 (45:53):
I never thought. I just assumed there would be in
the factory, like some sort of like vinegar mister hitting
the potatoes slices at some point.
Speaker 3 (46:01):
So I think some chips do use the powdered form
of acetic acid on salt and vinegar chips, but other
chips use malic acid. I was reading about this in
an article for the website Serious Eats by Dan Suza
called the Science behind Salt and Vinegar Chips. This guy
went through and studied the ingredients of a bunch of
different brands of salt and vinegar potato chips, and he writes, quote, surprisingly,
(46:24):
a couple of brands in our lineup opt for citric
acid from citrus fruits, malic acid from apples, lactic acid
from milk, or even fumeric acid which apparently comes from
lichen and the quote continues to give them pucker and punch.
So I was looking through which ones are the ones
(46:45):
that opt for malic acid. Some very familiar brands like lays,
Uts and Whys all use malic acid in their flavoring mix.
So it's not the only flavor there, but it's part
of the flavoring they use for the chip. And while well,
not all tartness is exactly the same, you know you'll
get different acidic types of flavors, and malic acid is
(47:07):
going to have a slightly different kind of tartness and
acidity than acetic acid from vinegar or citric acid. So yeah,
I don't know. I guess they just try different things
and figure out what flavors they like. But sometimes you're
going to be getting malic acid in your chips.
Speaker 2 (47:22):
Fascinating.
Speaker 3 (47:24):
So again, malic acid is all over the plant Kingdom.
It's not unique to cacti, but what makes it special
in the cresulation acid metabolism plants is that they use
it to store carbon resources during the off cycle. So
the carbon from the air is stored in the plant
(47:44):
as malic acid. It's brought in during the night and
then turned into malic acid stored there, and then once
the sun fires up in the daytime, the plant can
close its pores tight to protect its horde of water
and minimize evaporation, and then vert the malic acid back
into CO two inside its tissues and then fire up
(48:06):
the photosynthetic assembly line. So rough analogy, it's kind of
like having a form of cold storage. It's a place
you can store the materials you need when it's not
convenient to be getting them at the same time you're
using them.
Speaker 2 (48:18):
And it allows the day shift to continue the night
shift's work.
Speaker 3 (48:22):
Right. So, I was looking up some other examples of
camp photosynthesis and familiar plants, especially food crops, and it
turns out it just keeps popping up in interesting places.
(48:43):
Pineapples famously actually rely on cam Another plant that uses
camphotosynthesis to survive in dry conditions is the agave plant,
the juice of which is fermented and then distilled to
produce tequila. So anytime you have a marger rita, some
of the complex sweet and tart flavors that come from
(49:05):
the tequila element. Of course margarita, you're gonna have what's
the other stuff in there? I think orange, liqueur or
something and citrus. Yeah, but the tequila part itself, Some
of these flavors are downstream products of crasulation acid metabolism.
Another cam plant is vanilla. Now this one is not
(49:25):
fully cam. I'll discuss the distinction in a minute, but
this is interesting because the orchid flower that produces vanilla
vanilla beans doesn't grow in especially dry conditions like the desert.
It tends to grow in kind of, you know, moist
forest conditions like the dense, shady understory of a humid
(49:47):
tropical forest. So if the I was wondering, if its
environment is pretty wet, why does it need cam the
answer to this question. I had a harder time finding
a very clear CLI answer to this, and I was
seeing suggestions of different reasons in different sources. So maybe
it's kind of complicated, but it seems one possible part
(50:09):
of the answer brings us back to Kulchak, the nightstalker
and paramou Fa. So remember that Spanish moss is an epiphyte,
meaning it grows not on the ground but on the
trunks and branches of trees. And because it grows on trees,
it can't put roots into the ground to collect moisture,
so it has to collect moisture from the air and
(50:30):
directly from rainfall with these epiphytic roots or with these
things I think called tricombes on its outer tissues. So
this is a less stable, less dependable way to get
water compared to having roots sunk in the ground. Thus
it needs to use cam to protect what water it's
able to suck out of the fog and out of
(50:51):
the storm. Vanilla orchids are not full epiphytes, but it
seems they are semi epiphytes, so they do they have
roots in the ground, but they climb up trees. They
climb up the trunks and branches of trees like vines,
and as they climb up they produce these secondary aerial
(51:12):
roots to absorb water directly from the air and from
the rain. So kind of like Spanish moss, the aerial
roots are a less stable, less consistent way to harvest
water than the roots sunk in the earth, and so
this could be a reason why these vanilla flowers rely
on CAM at least in part. Could be other reasons too.
(51:34):
It might have to do with light and heat stress
in their hot environments, maybe as they like climb up
trees and become exposed to the sun. But whatever the reason,
when you taste vanilla, you can think about how wow,
you know? So the compounds that I'm tasting now are
downstream of growth through in part crysulation, acid metabolism. And
(51:58):
it's worth noting that the different photosynthesis pathways are not
mutually exclusive for a plant, so many plants can switch
between like direct C three photosynthesis and CAM depending on conditions.
It seems like vanilla orchids do this. A lot of
camplants use C three when water is abundant, and then
(52:20):
they switch defensively to the CAM pathway when they are
under thread of drought. This is called facultative CAM photosynthesis.
But the swaro is an interesting exception. It is one
of the rare plants that, as far as we can tell,
basically never goes into C three mode. It is pretty
much only CAM, which is called obligate camphotosynthesis and coming
(52:44):
back to the Jetman at All book, there's this whole
interesting section about this in a chapter by one of
the authors, Kevin Halteen. Halteen writes about some experiments that
demonstrate and study the suarro's obligate relationship to CAM. One
way you can do this is you put the soworro
inside an air type plexiglass box and then measure the
(53:06):
amount of CO two in the air in the box
over time. And sure enough, these experiments show that carbon
uptake by the sowarro is almost entirely confined to the
nighttime it's after midnight. In a period between midnight and
dawn and the rest of the day, carbon uptake is
either zero or it's actually negative. So during the day
(53:29):
it's you know, releasing carbon dioxide, which we don't usually
think of plants doing. So why would that be going on?
I guess there could be multiple reasons, but Holteine explains
that this is actually pretty common for cam plants during
the day because it happens when the malic acid is
inside the tissues is converted back into carbon dioxide, so
(53:51):
the photosynthesis can happen some of this co two escapes
from you know, it leaks out of the plant before
it can be converted into sugars. And another interesting thing
that they note is that the suaro shows differential carbon
uptake across the seasons of the year, regardless of some
objective external conditions like the amount of water present. This
(54:15):
seems to be an adaptation related to the fact that
they grow more in the summer and then they shift
into a more conservative, safer gas exchange strategy in the
off season when less new tissue growth is needed.
Speaker 2 (54:29):
Fascinating, fascinating. Yeah, there's such amazing engines really, you know, again,
it's so easy, especially with such a long living, slow
growing organism as this, to just think of them as
almost inert. You know, they're almost indeed like stone columns
holding up the sky. But they are very active in
(54:52):
what they're doing is amazing.
Speaker 3 (54:53):
Yeah, and so much of it is just centered around
gathering and protecting water resources. I mean, it's to psychologize
something that's actually just biological adaptation. It's like a water obsession,
you know, it feels like almost a religious orientation toward water,
which is a metaphor actually that you know that that's
(55:15):
not new to me suggesting here. You know, people think
of that often with desert organisms having a kind of
obsessive or religious devotion to the water and their environment.
It's what everything revolves around.
Speaker 2 (55:28):
Absolutely. Yeah, Now we're gonna go ahead and close out
this episode here, but we have a lot more to
talk about with the Sorrow, so well at least do
one more episode, and in the next episode of Belief,
we're going to get into indigenous traditions that involve the soarrow.
We're going to talk about some other animal interactions and
(55:51):
some other growth features of the soaro itself, So be
sure to tune in for that episode, and in the meantime,
certainly feel free to go ahead and ride in. Any
of you desert dwellers or desert tourists out there, or
cartoon watchers and Western officionados. We'd love to hear from
you as well, if you have thoughts on anything we've
(56:12):
discussed about the souaros thus far, or any media representations
and so forth. It's all fair game. Just a reminder
to everyone out there that Stuff to Blow your Mind
is primarily a science and culture podcast, with core episodes
on Tuesdays and Thursdays. Short form episode on Wednesdays and
on Fridays, we set aside most serious concerns to just
talk about a weird film on Weird House Cinema. Yes,
(56:34):
I'm not sure if we have watched a film with
the sowaro in it. We have watched some, We've watched
desert movies. We've watched Arizona movies, but I don't know
if we've watched anything filmed specifically in the Sonoran Desert.
I'd have to go back and check, but I'm not sure.
Speaker 3 (56:50):
I was going to say, I think there's some sowarro
in the movie Tarantula, the Okads Giant Spider movie that.
Speaker 2 (56:55):
Would make sense. Yeah, yeah, number of Arizona movies. I
need to go back and check. By Yes, bright In,
We'd love to.
Speaker 3 (57:01):
Hear from you huge thanks as always to our excellent
audio producer JJ Posway. If you would like to get
in touch with us with feedback on this episode or
any other, to suggest a topic for the future, or
just to say hello, you can email us at contact
a Stuff to Blow your Mind dot com.
Speaker 1 (57:23):
Stuff to Blow Your Mind is production of iHeartRadio. For
more podcasts from My Heart Radio, visit the iHeartRadio app,
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