Plants can recognize siblings

June 17, 2007 2:53 PM

According to a new study in Biology Letters (Royal Society journal), plants respond competitively when forced to share their pot with strangers of the same species, but when placed in a pot with their siblings are more accomodating. PDF, HTML.
posted by christopherious (41 comments total)

You know, I heard about this last week, and I still don't quite get how they're proposing that sibling plants recognize each other. Any experimental botanists want to explain?
posted by greatgefilte at 2:56 PM on June 17, 2007

Damn right. I ain't sharing my pot with no stranger. What if it's an undercover?
posted by nasreddin at 2:57 PM on June 17, 2007 [2 favorites]

This might clarify the thinking. From the full text (Discussion section): "Our results, because we used maternal sibships, indicate a genetic or maternally derived mechanism for kin recognition involving root communication. However, the mechanism is probably different from the self/non-self mechanism, because plants recognize genetically identical individuals as non-self."
posted by christopherious at 3:02 PM on June 17, 2007

Yes, well, how does 'root communication' work, then?
posted by greatgefilte at 3:02 PM on June 17, 2007

What is a pot to a plant? As long as there's enough dirt you can grow two plants in the same area.
posted by nervousfritz at 3:02 PM on June 17, 2007

(Forgot to mention I added the bold emphasis in that quote)
posted by christopherious at 3:04 PM on June 17, 2007

Yes, well, how does 'root communication' work, then?

According to this random site from a search: "The plant root is capable of secreting chemicals into the rhizosphere through root exudates. The chemical constituents of the root exudates are characteristic of a particular plant species and also depend on the surrounding biotic and abiotic environment. Recent research suggests that the root exudates act as a sort of chemical 'language' between the secreting plant and other organisms in the rhizosphere.". According to that site, this was taken from the Encyclopedia of Plant and Crop Science, published by Taylor & Francis this past April.
posted by christopherious at 3:08 PM on June 17, 2007 [1 favorite]

More details! I demand your finest details, I want them here and I want them now!
posted by greatgefilte at 3:10 PM on June 17, 2007 [1 favorite]

What is the implication of this? I can't really think of any. Could scientists use genetic engineering to make crops 'play together' more nicely?
posted by delmoi at 3:14 PM on June 17, 2007

The linked article cites Mahall, B.E. & Callaway, R.M.'s "Root communication mechanisms and intracommunity distributions of two Mojave Desert shrubs."

From the abstract:

"Experimental studies using root observation chambers to observe the effects of encounters between individual roots on root elongation rates have revealed that the interactions among roots of Ambrosia dumosa and Larrea tridentata are more complex than simple competition for a limiting resource. Larrea roots inhibited elongation of either Larrea or Ambrosia roots in their vicinity, and Ambrosia roots inhibited elongation of contacted roots on other Ambrosia plants only.

[. . .]

These results support the hypotheses that the interaction mechanism of Larrea roots involves the release of a readily diffusible, generally inhibitory substance by Larrea roots into the soil, rather than a simple depletion of water or nutrients from around Larrea roots, and that the intraspecific, self—nonselfish—recognizing interaction mechanism of Ambrosia roots is mediated by contact and is fundamentally different from that of Larrea."

(This sort of knowledge could be potentially be used to genetically engineer crops that naturally repel 'weed' species or just to better understand how ecosystems work. Or even to make crops play nicely together.)
posted by Matt Oneiros at 3:20 PM on June 17, 2007

Could scientists use genetic engineering to make crops 'play together' more nicely?

Or, you could theoretically increase crop yields by identifying groups of plants that play nice with each other. Plant the corn with the radishes to make more corn. But don't put the lettuce near the oranges, or you'll get Jets vs. Sharks rumbles, followed by a few dippy musical numbers, and then someone offs Maria's boyfriend ... duh-nu-nuh-nunna-nuh-'merIca, duh-nu-nuh-nunna-nuh-'meriCAH...
posted by frogan at 3:28 PM on June 17, 2007

delmoi, it's quite significant from a theoretical point of view. It's known that some plants are 'self-sterile,' that is, if a plant attemps to become fertilized by its own pollen (or, apparently, pollen of a closely related plant of the same species), it doesn't work. But this paper implies something completely different, that somehow the roots of each individual plant can recognize and discriminate between sibling and non-related fellow plants and adjust root growth appropriately to either aggressively compete for resources (in the case of a non-related plant) or to co-exist (with a related plant). How on earth are they doing that? We tend to think that plants of the same species are generally very similar to each other ("they all look the same!"_, but apparently the plants know better.
posted by greatgefilte at 3:31 PM on June 17, 2007

But again I think that aggressively compete is being blown out of proportion here, you probably couldn't find plants that get as aggressive as chimpanzees would.
posted by nervousfritz at 3:35 PM on June 17, 2007

Mama always knows: "Heliotrope, let Daisy have some sun ... or it'll be lights out for you!"
posted by rob511 at 3:38 PM on June 17, 2007

Well, with plants prefering their relatives and whatnot, I'd like to know what the vegetarians have to say. What are they going to eat once we admit that plants have feelings too?
posted by Hildegarde at 3:56 PM on June 17, 2007

Maybe they'll eat only voluntarily donated human flesh.
posted by Justinian at 4:04 PM on June 17, 2007

These vegetarians, do they bite?
posted by CautionToTheWind at 4:21 PM on June 17, 2007

I noticed this phenomenon in my vegetable garden.

Selfish beans!
posted by UbuRoivas at 4:35 PM on June 17, 2007 [1 favorite]

It's intriguing: how selective is this recognition (i.e. can it tell a cousin from a brother? a brother in a field of 100 strangers?)

By what mechanism? siRNAs? Cocktails of plant pheromones? Actual genetic sequence recognition?


....
posted by lalochezia at 4:40 PM on June 17, 2007

Hildegarde: Funny if you're not being serious, but if you are, come on. Automated genetic processes are somehow just sort of sentience?

Anyway, a huge majority of plant matter eaten by human beings is intended to be consumed. Oops, I meant that that's its purpose. Damn those sentient plants, scheming sentiently to make us eat their fruit.
posted by invitapriore at 4:46 PM on June 17, 2007

As Arthur C. Clarke said, sufficiently intelligent design is indistinguishable from sentience.
posted by nowonmai at 5:09 PM on June 17, 2007 [1 favorite]

Automated genetic processes are somehow just sort of sentience?

What's an "automated genetic process" and how does that differ from the machinery inside your own cells?

It has long been known that plants respond to stimuli, and even communicate with each other. So why is a shellfish less deserving of protection than plants?

Anyway, a huge majority of plant matter eaten by human beings is intended to be consumed. Oops, I meant that that's its purpose.

So is the majority of animal matter consumed by humans.
posted by grouse at 5:12 PM on June 17, 2007

OMG. I've been a Metafilter member seven years and I had to wait this long for a plant root ecology post!

Self/non-self recognition of roots is very much a still poorly understood aspect of plant growth, and also an active field of research, involving lots of fun experiments splitting plant shoot and root systems and growing them in the same pots etc. And it is mainly important from a theoretical point of view - I don't think there are grand aims for starting a new Green Revolution out of all this. A lot of the implications lie in ecology and plant competition:

- How do roots compete for resources with other roots of the same plant?
- What are the implications of this for the dynamics and spatial arrangement of root growth?
- How about competing with roots of a different individual of the same species?
- How about competing with roots of a different species?
- And what are the implications of this for the spatial arrangement of plants?
- How do we get over-dispersed patterns in some ecosystems?
- What's the most efficient way to use the resources present?

I saw an interesting paper presented a few years ago, but I can't really remember the gist of it or who it was by. If I remember correctly, they did split-root experiments with clones - plants that were genetically identical. If the plant was all in one piece the roots of the two sections avoided each other. If they then cut the plant in two, the roots competed with each other. This suggested that some non-genetic mechanism was at play - the roots from one side of the plant were "talking" to the roots from the other side to coordinate their growth!

Sorry, I did a PhD on shit like this. I'm allowed to get excited once ina while.
posted by Jimbob at 5:15 PM on June 17, 2007 [3 favorites]

Gee, maybe now scientists will pay attention to what gardeners have been saying for years: some plants seem to get along very well when planted near each other, and some plants just don't, i.e. the art of companion planting. Gardening folklore tips like "roses love garlic" and "rue hates basil" have been around for hundreds of years or longer. One of the Pliny's (not sure which one), the great natural philosophers of ancient Rome, talked about how "rue and the fig tree are in great league and amitie together" because they enhance each other's growth if planted close together. I've got gardening books on my shelves chock full of sayings like "do not plant sage with cucumber, which does not like aromatic herbs in general, and sage in particular". You get the idea.

Another example: "tomatoes like marigolds" was probably thought to be just more garden folklore, despite the rule's long history of being observed in French potagers (kitchen gardens) -- until scientists "discovered" just a few years ago that marigolds actually do release chemicals into the soil that impede and/or prevent the formation of nematodes in the tomato roots. And another example: it's long been said that planting hyssop near grape vines increases the grape yields. Guess what, more and more winemakers seem to think it works too and are turning to the practice.

So, yeah, great news that the Botany article is starting to raise scientists notice of the "companion planting" phenomena, but, honestly, if they bothered to mention their findings on GardenWeb.com's forums or among a group of nice retiree organic gardeners, I think the general reaction would have been "well, duh."
posted by Asparagirl at 5:17 PM on June 17, 2007 [3 favorites]

Yes, well, how does 'root communication' work, then?

Yeah, still very much the big question. Sure, roots produce chemical exudates, which clearly have a role to play in competition and self/non-self recognition. But experiments like this show that there is still much to learn. And, indeed, the experiment I (poorly, and possibly wrongly) described above suggests an intra-cellular mechanism of root growth coordination as well.
posted by Jimbob at 5:20 PM on June 17, 2007

So, yeah, great news that the Botany article is starting to raise scientists notice of the "companion planting" phenomena, but, honestly, if they bothered to mention their findings on GardenWeb.com's forums or among a group of nice retiree organic gardeners, I think the general reaction would have been "well, duh."

Yes! Damn those scientists for not listening to the gardeners! I doubt you've done a good review of the scientific literature on the subject, because this stuff has been studied by SCIENTISTS for a long, long time. The tomato / marigold example you cite doesn't prove that scientists have been ignorant of the phenomenom, it just shows that scientists have been looking for the mechanism behind the interaction. Because...you know...that's their job. Finding out why stuff works... Which they did.
posted by Jimbob at 5:24 PM on June 17, 2007

Damn those scientists for not listening to the gardeners sooner!

Fixed that for you. :-)

The tomato / marigold example you cite doesn't prove that scientists have been ignorant of the phenomenom

It was a nice thing to see finally proved scientifically, after so many years of in-ground practice. But before any scientists bothered to test the hypothesis that "tomatoes like [i.e. grow better when placed near] marigolds", how many of them were either ignorant of the saying or of the practice or were rolling their eyes at the gardeners who may have mentioned it? Why did it take until the late 1990's for someone to finally do a controlled test of a gardening technique that's been in use for maybe hundreds of years?

Finding out why stuff works...

Which is a very good thing, I'm agreeing with you here! Knowing the 'why' is a great thing! But I think -- and perhaps this is unfairly colored by the discussion here at MeFi -- that this paper is not just saying 'this is why', beacuse they're not entirely sure of the mechanism of the 'why' just yet. They're simply stating that 'this phenomena exists', and like I said, that's not exactly news to any gardening club.
posted by Asparagirl at 5:39 PM on June 17, 2007

phenomena phenomenon

Doo doo, duh-doo-doo.
posted by Asparagirl at 5:42 PM on June 17, 2007

Asparagirl, it's just that the theme of your comment seemed to be "Scientists have been ignoring the fact that different species of plants interact with each other in different ways, when gardeners have known this for centuries".

Whereas I have a drawer of papers here, going back close to a century in some cases, where scientists have been studying the intra- and inter-specific interactions of plants. It is a fundamental question of ecology, and has been for a long, long time. Scientists didn't just discover that plants react to their own species differently than other species last week - this really has been a long running and contentious field of study for a long time.

Sure, maybe they haven't focused on specific examples that are relevant to your vegie patch. I propose that this might be because the majority of studies have either been in natural ecological systems, or have been based around model plant species in experiments. The agricultural scientists / horticultural scientists who should have addressed the marigold / tomato question sooner might have been busy inventing dwarf wheat or something.
posted by Jimbob at 5:44 PM on June 17, 2007

The 'marigolds love tomatoes' stuff is a completely different thing from this new, intra-specific competition and self/non-self recognition. It's not that scientists have finally jumped on the bandwagon, it's that these particular scientists have discovered something entirely new.
(On preview, deleted much of this comment because Jimbob is more articulate and knowledgeable, but I was trying to say what he said).
posted by nowonmai at 5:49 PM on June 17, 2007

I find the idea that kin selection, an altruistic behaviour, works with plants, philosophically fascinating. This is at the core of what evolutionists have been saying, altruism and by extension good behavior is an evolutionary response ie. morality is natural, it doesn't have to come from an outside source (such as God, or the legal system, or education). Altruistic behavior as part of natural selection has been demonstrated in higher animals but to see it operating in plants is both astounding and not surprising, but certainly a huge validation of evolutionary ideas.
posted by stbalbach at 5:56 PM on June 17, 2007

OMG. I've been a Metafilter member seven years and I had to wait this long for a plant root ecology post! [...] Sorry, I did a PhD on shit like this. I'm allowed to get excited once in a while.

Hm, would you be familiar with this miscreant at all?
posted by UbuRoivas at 6:06 PM on June 17, 2007

grouse: Well, it's a difficult line to draw. I don't really even know what we're arguing about here, except for the vague notion that someone is against vegetarianism and someone is for it, maybe. Either way, I'm talking about sentience, which your example of shellfish quite rightly shows is not even a characteristic of all animals. So?

As for animal flesh being intended for consumption, well, you're being a little literal, eh? The plant produces fruit that may be consumed so that it might propogate its seeds. I don't think there's an animal alive that (as an individual) has any positive investment in getting eaten, even though it may serve quite well as a source of food for another species.

All I meant to communicate initially was that the "why don't you feel bad about killing the poor plants" argument against vegetarianism is a tired one, even when brought out in humor.

But more on topic, stbalbach, what I wonder (and what you brought up) is why is kin selection an advantageous behavior for a plant? They're essentially on their own in the world, so how does working with a sibling and not a stranger in a situation of such limited resources confer any benefit to them?
posted by invitapriore at 7:31 PM on June 17, 2007

Yes indeed, Ubu, I've met and had a cuppa with Huw at a couple of conferences in fact!
posted by Jimbob at 7:57 PM on June 17, 2007

As for animal flesh being intended for consumption, well, you're being a little literal, eh?

It is the only way to make sense out of a claim that plants have a "purpose" in producing fruit. As you wryly point out, the plants cannot possibly intend that their fruit be eaten. It is only as a result of years of evolution that some plants produce tasty fruit.

In the same sense, domesticated animals derive a significant evolutionary advantage because humans desire to convert them into food. An animal that produces less food or less tasty food is less likely to pass on its genetic material.

why is kin selection an advantageous behavior for a plant? They're essentially on their own in the world, so how does working with a sibling and not a stranger in a situation of such limited resources confer any benefit to them?

Just as in animals, selection in plants is all about the likelihood of alleles being passed on to another generation, not primarily about the longevity of an existing individual, which is going to die in the long run anyway. For both plants and animals, aiding relatives will increase the likelihood of some shared genetic material surviving, even if it is at the expense of an individual. A population of kin-helping plants outsurvived a population of kin-hindering plants, despite some of the kin-helping plants making the ultimate sacrifice.
posted by grouse at 8:03 PM on June 17, 2007

what I wonder (and what you brought up) is why is kin selection an advantageous behavior for a plant? They're essentially on their own in the world, so how does working with a sibling and not a stranger in a situation of such limited resources confer any benefit to them?

It's part of "selfish gene" theory. Your sibling carries the same genes as you. If your sibling survives to procreate but you do not, those genes are still transmitted to subsequent generations. Altruism towards siblings & other relatives has been well documented in the biological sciences, and this is one explanation for the phenomenon.

On preview: Jimbob: you'd be happy to hear then, that he's currently on his bicycle, somewhere between Paris & Tallinn.
posted by UbuRoivas at 8:04 PM on June 17, 2007

update: somewhere between Paris Český Krumlov & Tallinn
posted by UbuRoivas at 8:12 PM on June 17, 2007

In the same sense, domesticated animals derive a significant evolutionary advantage because humans desire to convert them into food. An animal that produces less food or less tasty food is less likely to pass on its genetic material.

On the other hand, domesticated animals have been held in captivity for a very short period of time — almost insignificant. Their recent evolutionary "success" (as measured by being desirable enough to eat in the last 5000 years that we help them reproduce) is predicated on being docile enough to breed, raise and slaughter, not by how delicious they taste to some people.

Consider the blowfish, for example: held by some as a delicacy, but dangerous to catch and prepare. Certainly not a domesticated species.

The taste of animal meat seems independent of evolutionary factors: for some it is pleasant, but the taste is itself entirely coincidental.
posted by Blazecock Pileon at 10:17 PM on June 17, 2007

Yes, you are right, Blazecock Pileon. I think I was unclear about what I meant—that domesticated animals that taste good and especially that produce more meat are more likely to survive than other domesticated animals.

The taste of animal meat seems independent of evolutionary factors:

Well, I think you mean independent of selection, since taste definitely seems to descend with modification like other phenotypic characters, as shown in this classic paper, where the author hypothesizes where different tastes arose in evolutionary history. But I still think that taste is important for selection in domesticated animals. If an animal is kept for food purposes, and it tastes bad, smart farmers aren't going to let it reproduce. I agree that taste to humans is an unimportant character for most animals, and that some plants and animals derive an advantage from tasting bad to predators.
posted by grouse at 2:09 AM on June 18, 2007

Whoa, it's pretty crazy to think that, say, a field of corn is not just a whole bunch of individual corn plants, but rather families of corn plants, living together in one field, vying for resources, trying to ensure the success of their respective clans.

It's good thing I'm not stoned right now, is all I'm saying.
posted by LordSludge at 12:53 PM on June 18, 2007

How hard is this? It benefits the gene to respect the gene. This is so Dawkins 101.
posted by Toekneesan at 4:35 PM on June 18, 2007