Do Plants Think?

By | June 6, 2012

Do Plants Think

Scientist Daniel Chamovitz unveils the surprising world of plants that see, feel, smell—and remember

How aware are plants? This is the central question behind a fascinating new book, “What a Plant Knows,†by Daniel Chamovitz, director of the Manna Center for Plant Biosciences at Tel Aviv University. A plant, he argues, can see, smell and feel. It can mount a defense when under siege, and warn its neighbors of trouble on the way. A plant can even be said to have a memory. But does this mean that plants think — or that one can speak of a “neuroscience†of the flower? Chamovitz answered questions from Mind Matters editor Gareth Cook. …

It had been known for decades that plants use light not only for photosynthesis, but also as a signal that changes the way plants grow. In my research I discovered a unique group of genes necessary for a plant to determine if it’s in the light or in the dark. When we reported our findings, it appeared these genes were unique to the plant kingdom, which fit well with my desire to avoid any thing touching on human biology. But much to my surprise and against all of my plans, I later discovered that this same group of genes is also part of the human DNA.

This led to the obvious question as to what these seemingly “plant-specific†genes do in people.  Many years later, we now know that these same genes are important in animals for the timing of cell division, the axonal growth of neurons, and the proper functioning of the immune system.

But most amazingly, these genes also regulate responses to light in animals! While we don’t change our form in response to light as plants do, we are affected by lab at the level of our internal clock. Our internal circadian clocks keep us on a 24 hour rhythm, which is why when we travel half way around the world we experience jet lag. But this clock can be reset by light. A few years ago I showed, in collaboration with Justin Blau at NYU, that mutant fruit flies that were missing some of these genes lost the ability to respond to light. In other words, if we changed their clocks, they remained in jetlag.

This led me to realize that the genetic difference between plants and animals is not as significant as I had once naively believed. So while not actively researching this field, I began to question the parallels between plant and human biology even as my own research evolved from studying plant responses to light to leukemia in fruit flies. …

There is no doubt that plants respond to cues from other plants. For example, if a maple tree is attacked by bugs, it releases a pheromone into the air that is picked up by the neighboring trees. This induces the receiving trees to start making chemicals that will help it fight off the impending bug attack. So on the face of it, this is definitely communication. …

Plants definitely have several different forms of memory, just like people do. They have short term memory, immune memory and even transgenerational memory! …

For example a Venus Fly Trap needs to have two of the hairs on its leaves touched by a bug in order to shut, so it remembers that the first one has been touched. But this only lasts about 20 seconds, and then it forgets. Wheat seedlings remember that they’ve gone through winter before they start to flower and make seeds. And some stressed plants give rise to progeny that are more resistant to the same stress, a type of transgenerational memory that’s also been recently shown also in animals. While the short term memory in the venus fly trap is electricity-based, much like neural activity, the longer term memories are based in epigenetics — changes in gene activity that don’t require alterations in the DNA code, as mutations do, which are still passed down from parent to offspring. …

Would you say, then, that plants “think�
No I wouldn’t, but maybe that’s where I’m still limited in my own thinking! To me thinking and information processing are two different constructs. I have to be careful here since this is really bordering on the philosophical, but I think purposeful thinking necessitates a highly developed brain and autonoetic, or at least noetic, consciousness. Plants exhibit elements of anoetic consciousness which doesn’t include, in my understanding, the ability to think.  Just as a plant can’t suffer subjective pain in the absence of a brain, I also don’t think that it thinks.  …

Do you see any analogy between what plants do and what the human brain does? Can there be a neuroscience of plants, minus the neurons?
First off, and at the risk of offending some of my closest friends, I think the term plant neurobiology is as ridiculous as say, human floral biology. Plants do not have neuron just as humans don’t have flowers!

But you don’t need neurons in order to have cell to cell communication and information storage and processing.  Even in animals, not all information is processed or stored only in the brain. The brain is dominant in higher-order processing in more complex animals, but not in simple ones.  Different parts of the plant communicate with each other, exchanging information on cellular, physiological and environmental states. For example root growth is dependent on a hormonal signal that’s generated in the tips of shoots and transported to the growing roots, while shoot development is partially dependent on a signal that’s generated in the roots. Leaves send signals to the tip of the shoot telling them to start making flowers.  In this way, if you really want to do some major hand waving, the entire plant is analogous to the brain. ….

But while plants don’t have neurons, plants both produce and are affected by neuroactive chemicals! For example, the glutamate receptor is a neuroreceptor in the human brain necessary for memory formation and learning. While plants don’t have neurons, they do have glutamate receptors and what’s fascinating is that the same drugs that inhibit the human glutamate receptor also affect plants. From studying these proteins in plants, scientists have learned how glutamate receptors mediate communication from cell to cell. So maybe the question should be posed to a neurobiologist if there could be a botany of humans, minus the flowers!

Darwin, one of the great plant researchers, proposed what has become known as the “root-brain†hypothesis. Darwin proposed that the tip of the root, the part that we call the meristem, acts like the brain does in lower animals, receiving sensory input and directing movement. Several modern-day research groups are following up on this line of research. …

via Do Plants Think?: Scientific American.

3 thoughts on “Do Plants Think?

  1. Baldscientist

    Reblogged this on Baldscientist and commented:

    Very interesting! The idea of “Plant Neurobiology” has recently been proposed as serious research; there are even scientific meetings and books on the subject. I wrote a blog post not so long ago if you are interested to know a little more about it…

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