Monday, January 20, 2014

Are plants altruistic?

A friend has been urging us to read Michael Pollan's piece ("The intelligent plant" in the Dec 23 issue of The New Yorker since it came out last month.  Finally, on the plane to sunny Arizona, I got around to reading it, and fascinating and thought-provoking it is.  Here on MT we always appreciate a story that looks around the corners, and this one is a fine example of just that.

The story, in essence, is that plants do things that strike a lot of people as intelligent.  Even people who are unwilling to use that word are willing to admit that there may be more to plant behavior than has previously been thought.  The argument, gaining prominence in a 2006 paper in Trends in Plant Science that proposed a new field called plant neurobiology (according to Pollan, rather recklessly), is that plants respond to so many environmental conditions in coordinated ways that it looks suspiciously as though there is some sort of central processor that does the coordinating.

Plants perceive and respond to light, temperature, toxins, gravity, crowding, insect attack, microbes, nutrients in the soil, soil structure and many other environmental variables with chemical and hormonal changes, and this has long been known. And, it has long been known that plants have systemic responses, and even -- though this has been more controversial -- that they can convey information to other plants, and that other plants have the ability to sense incoming signals.

There is increasing evidence that these responses are more than simple, local chemical reactions. And that, indeed, some are homologous to responses in animals and even involve some of the same neurotransmitters.  Many plant biologists are still reluctant to think in terms of plant neurobiology, however, primarily because plants don't have neurons.  Or brains.

Indeed, even proponents don't argue that there's a heretofore unrecognized central nervous system or processor hidden somewhere inside the plant, but they do argue that the chemical signaling that goes on can be systemic, and that a plant's whole system of root tips may, as Pollan writes, be capable of "gathering and assessing data from the environment and responding in local but coördinated ways that benefit the entire organism."

Excitable cells just behind the root tip have been found to have high levels of electrical activity and oxygen consumption, and this may be in some way the equivalent of a brain in the sense of information-processing.  Pollan writes,
How plants do what they do without a brain—what Anthony Trewavas has called their “mindless mastery”—raises questions about how our brains do what they do. When I asked Mancuso about the function and location of memory in plants, he speculated about the possible role of calcium channels and other mechanisms, but then he reminded me that mystery still surrounds where and how our memories are stored: “It could be the same kind of machinery, and figuring it out in plants may help us figure it out in humans.” 
The hypothesis that intelligent behavior in plants may be an emergent property of cells exchanging signals in a network might sound far-fetched, yet the way that intelligence emerges from a network of neurons may not be very different. Most neuroscientists would agree that, while brains considered as a whole function as centralized command centers for most animals, within the brain there doesn’t appear to be any command post; rather, one finds a leaderless network. That sense we get when we think about what might govern a plant—that there is no there there, no wizard behind the curtain pulling the levers—may apply equally well to our brains.
And, indeed, brains are just chemical and electrical responses to the environment, too.  Somehow, in aggregate, this processing leads to 'mind' in at least some animals.

Here's a video, narrated by Pollan, showing an example of one of the behaviors that plant behavior people are trying to make sense of.  The bean plants seem to be striving to find the pole that has been planted just outside their reach.  Pollan makes the important point that plant behavior happens on a much slower time scale than we can observe, and that time lapse photography is what has made this new view of their behavior possible.  Images of these growing plants were taken every 10 minutes, which makes it possible for us to see -- or imagine -- that the plant is striving to reach a goal.

Roots have also been found to seek out underground water pipes, even when the exterior of the pipe is dry, suggesting to researchers that the roots are somehow responding to the sound of flowing water.

The whole underground world of intertwined, communicating roots seems to be one that we've only just started to understand.  Roots can distinguish self from other, and they know their own kind (species), they can share resources and information about insect attacks and deliver nutrients to trees in need.  The preponderance of evidence does seem to suggest that plants are proactive in filling their own needs and the needs of others.

Pollan's beautifully written piece raises many intriguing questions and issues, and certainly not only about plants.  Among them, what is intelligence?  What is is a brain?  What is an organism?  We've long thought of plants in the same way we think about animals, as in competition for sun and soil nutrients, but now it seems that there's a lot of cooperation going on, and we even must ask whether plants, too, can be altruistic.  And, the whole group selection question, whether an organism can evolve to behave for the good of the group rather than itself alone, will probably need to be revisited.

Plant intelligence is something we've touched on in the past.  Of course, an over-riding issue for many biologists is the mysterious origin and nature of consciousness, which is not the same as neural information processing or problem-solving.  We have in one of our books mused about whether there is some sort of organismal awareness in a plant or among plants, for example, whether the totality of a tree's leaves constitutes an analog of a retina in an animal eye, giving an overall 'image' of the light environment.  But one has to be careful about terms and wording, and not to be suggesting (without a lot more evidence than we know of today) that plants have any sort of awareness that we would recognize as similar to our own experiences.

And finally, here are three odes to the carrot that we posted back in 2011.  It seems like a good time to reprise them here.  Again we thank Gary Greene, a poetically-inclined MT reader, for his poem, his permission to post it here, and the inspiration it gave us to write our own.

By Gary Greene

Carrots that feel, beets that pine,
Are they rooted in awareness,
These veggies of mine?
When arrayed at the store,
Is it dirt that they dish?
Can onions and potatoes
Make a vegetable wish?
Would they choose life in the ground,
Until they lay rotten?
Or to be served up in bowls,
Sauteed or au gratin?
Do they think deeper thoughts,
the deeper they grow?
Do they plan for the future,
or just wait for snow?
When the frost comes early,
do they think warmer things?
And at night, if they dream,
take flight on veggie wings?
We may never know
if veggies are aware,
if they think lofty thoughts,
or simply don't care.
It's so hard to tell,
there's nothing to do,
but pass the green peas,
and the turnip greens, too!

By Ken Weiss


A carrot is a thoughtful thing,
That worries what the rain will bring.
With all its neighbors, sore it grieves,
The gruesome gnawing on its leaves.

Of peas we could the same relate,
And from the lettuce, no debate.
The Fall's last katydid doth moan,
Unanswered calls: it's all alone.

These plaintive cries unnoticed, all,
By humans: blinded to the pall,
And hearing naught, can naught believe.
So, voiceless, plants no pathos leave.

We spare no thoughts for 'thoughtless' being,
Assuming only we are seeing,
Yet trees observe the sun all day,
With leafy retinal display.

We grant no ‘self’ to fish nor fowl,
Hard-wired deem the lions growl.
Thus poems are writ by fools like me,
Who can’t converse with ant, or tree.

By Anne Buchanan

I just hope
carrots don't dream.

But if they do
I hope they don't
of having
to run away

Legs and hips and feet,
in our image.
And arms to raise themselves
from the earth.

If they
were made in
our image,
not only would
feel fear, but
they would
have to confront
the ethical dilemma
of whether
or not
to eat themselves.


Anne Buchanan said...

Ah yes, I note that I didn't directly address the title of the piece in the post. Are plants altruistic? It's interesting to muse about, and Pollan's piece provides the fodder for doing so. The observation that plants can provide nutrients to other plants that need them, kin and even non-kin, that they warn of insect invasions, and share nutrients in root-based communication systems and so on suggests that, as with intelligence, we might have to broaden our view of altruism. It has long been considered a sticking point in evolutionary theory, at least by strict darwinians. If even plants help each other out, however, altruism starts to look like a more widespread and perhaps fundamental characteristic of life.

Ken Weiss said...

Altruism has formally been related to kinship relationships in a sensible way, but often too rigorously or with too strongly selectionistic a viewpoint (since most local conspecifics may be kin, kin-selection would be rather automatic if individuals just help conspecifics). If a bird or chipmunk calls when it spots a cat, this alerts its conspecifics to the danger, another altruism issue (since the calling bird puts itself in danger). But, and this is not something I've seen discussed before, it also enables members of other species to know the predator is there--a kind of community warning system, but whether that has evolutionary implications of its own is not something I've seen any discussion of.

Robert Kopec said...

Herbert Spencer Jennings (Behavior of the Lower Organisms, 1906 [] ) would have loved this discussion and the Pollan video. Thanks for sharing.

Anne Buchanan said...

Thanks so much for this excellent resource! I am going to dip into it right now.

Manoj Samanta said...

A very talented Bengali scientist did similar research 100+ years back, but nobody wanted to believe him.

"His books include Response in the Living and Non-Living (1902) and The Nervous Mechanism of Plants (1926)."

He is not the same Bose as the one who corrected Einstein's equation and got his name on a fundamental particle.

Robert Kopec said...

Didn't know about him, but inspired by your comment found that he also invented the crescograph, a device that with wires connected from the plant to a timing mechanism measured how fast plants grew each hour. As a plant grew, the movement was recorded on smoked glass.

Was also one of the early researchers on wireless transmission of electrical impulses.

And was one of the pioneers of science fiction writing, with a story of how a bottle of baldness treatment oil, of the brand that sponsored the writing contest he entered, dissipated a cyclone, thus saving the city of Calcutta.

Manoj Samanta said...

Yes, he apparently invented telegraph radio communication system before Marconi, but did not get Nobel or patent for not being in the right circles.

That is what we were taught in school, but I have no idea how much of that is correct. On one hand, the commies, who wrote our school text-books were habitual liars, and I have difficulty believing anything they taught us in school. On the other hand, British Calcutta had very vibrant scientific culture and produced several very high-quality scientists. J. C. Bose was the most creative among them.

Anonymous said...

He actually rejected the idea of patenting science. Or of keeping knowledge secret in the interest of personal gain. A precursor of open source technology? The question, by the way, of what is an organism interested him. Seems he saw a continuum between inanimate minerals and living organisms.

Ken Weiss said...

Well, there is only one real world, one presumes. Life began by spontaneous generation of a sort, we also presume as scientists. Perhaps a unitary worldview is consistent with this, a form of one might say Buddhist thinking. If one didn't take it too far! Do you know Tellhard de Chardin or Henri Bergson? They made efforts like that, as did some of the Greeks. The great search for causal unity, one could say.

Manoj Samanta said...

Hermann Hesse's beautiful novel Siddhartha also highlighted that continuum between inanimate minerals and living organisms. He saw the continuum through living objects and natural objects going through periodic cycles (just like humans live, grow up, get old and die, water goes through cycles of rain--> ponds --> river --> ocean --> moisture).

I have been reading Stphen Jay Gould's books and found his 'punctuated evolution' theory quite thought-provoking. If every living animal goes through birth and death, it is not a stretch to imagine that a species will experience birth, 'stasis' and death as part of natural process.

Ken Weiss said...

I'd be careful about 'punctuated equilibria' because it has been controversial and over-used. How 'punctuated' life actually is, as opposed to the fossil record, is not so clear. For example, some traits may be conserved (til they change!), but the underlying genome continues to click (the molecular clock) and the genes themselves may evolve. So p-e can be a slogan that is over-interpreted. Still, these are issues of relevance, for sure.

Manoj Samanta said...

Coming from physics background, such things do not bother me. When we add heat to a material at critical point, its atoms continue to increase vibrations or other heat-related activities, but externally the heat seems to disappear in a black hole (latent heat). Then all of a sudden, ice turns into water - a completely different form. Essentially, we need to find the link between changes in genes and changes in phenotype at the system level, and that is the hardest part. All pieces of the machine were barely identified 5-10 years back.

I guess Stuart Kauffman and rest of Santa Fe school tried to bring some of those ideas of complexity theory into biology. However, it is one thing to speculate on a potential mechanism and another thing to demonstrate the same with proof.

Ultimately we come to the same conclusion - life is far more complex than the human geneticists want us to believe. At least I am starting to see all layers of the onion, unlike in the past.

Ken Weiss said...

In a sense, a change in a gene is always a punctuation event--a discrete change, between which faithful transmission is 'equilibrium'. But when there are collectives (many individuals in a species, and many species) it is less clear how this extends. I think most would use the term 'emergence' for it, and perhaps what happens in an ecosystem is a form of 'phase transition'. Or perhaps it is a wavelike phenomenon in someway that we don't understand. I was affiliated with the Santa Fe Institute for several years as an external faculty member, and while there were (and are) many very smart people there, working on complex problems, I think the major breakthroughs, if any are in fact possible,haven't occurred. Your final paragraph is a good summary of present knowledge.

Robert Kopec said...

Not really familiar with de Chardin or Bergson. Do recall as a teenager, many decades ago, learning that de Chardin was instrumental in getting the Catholic Church and people of other religious persuasions to accept a qualified modus vivendi with Darwin. On Bergson, will have to put him on my to-read list.

On life, wasn't there once, or maybe still is, a question as to whether viruses are living somethings, or are in that fuzzy area between the living and the not?

Ken Weiss said...

Viruses are RNA or DNA coated with protein, basically. They only do anything when in some host cell. So they are not 'alive' but are part of life.

Chardin's book The Phenomenon of Man tried to build a cosmos in which an essence of life was in everything even atoms, as I recall. Humans were higher on the scale and Omega was the cosmos or God himself--something like that. But as I recall the Church banned the book, at least for a long time.

Bergson's somewhat similar idea was that objects have some inherent life, an elan vital as he called it. You can find out more by Googling him, I'm sure.

Jennifer said...

plants do all kinds of cool stuff without brains and I loved Michael Pollan's video of the bean plants. But so do one celled beings - amoeba, for example. And, carrots wondering about whether to eat themselves, if they were more humanlike - humans have wondered the same thing and some do, some don't. I wonder what carrots would decide.

Ken Weiss said...

The only issue is that carrots don't 'eat' in the same sense. They absorb chemicals from the earth and air, so they would have to absorb another carrot; I don't know if that's possible unless the other one is dead.