A new relationship with animals, nature and each other.

Do Plants Think?

Turns out they’re not just potted plants

plants-communicate-060612In a testy exchange at a Senate hearing about the Iran-Contra scandal in 1987, Col. Oliver North’s attorney Brendan Sullivan said to Senator Daniel Inouye, who he thought was trying to muzzle him, “Well, sir, I’m not a potted plant.”

Twenty-five years later, it turns out that plants, potted or otherwise, aren’t just potted plants, either.

In his new book, What a Plant Knows, Daniel Chamovitz, director of the Manna Center for Plant Biosciences at Tel Aviv University, says they can see, smell and feel – not in the same way as animals, obviously, but certainly their own way.

For example, the same set of genes that regulate the circadian patterns in us humans are present in plants, where they regulate the plants’ responses to light.

Here are some excerpts from an interview in the blog Mind Matters:

If we realize that all of plant biology arises from the evolutionary constriction of the “rootedness” that keep plants immobile, then we can start to appreciate the very sophisticated biology going on in leaves and flowers. Plants can’t escape a bad environment, can’t migrate in the search of food or a mate. So plants had to develop incredibly sensitive and complex sensory mechanisms that would let them survive in ever changing environments.

If you’re hungry or thirsty, you can walk to the nearest watering hole (or bar). If you’re looking for a mate, you can go out to a party. But plants are immobile. They need to see where their food is. They need to feel the weather, and they need to smell danger. And then they need to be able to integrate all of this very dynamic and changing information. Just because we don’t see plants moving doesn’t mean that there’s not a very rich and dynamic world going on inside the plant.

whataplantknows_chamovitz-060612On how plants have a sense of smell: A parasitic plant called dodder finds its food. Dodder can’t do photosynthesis, and so has to live off of other plants. The way it finds its host plant is by smelling. A dodder can detect minute amounts of chemicals released in the air by neighboring plants, and will actually pick the one that it finds tastiest. In one classic experiment scientists showed that dodder prefers tomato to wheat because it prefers the smell.

On hearing: Much of the research on music and plants was not carried out by investigators grounded in the scientific method. But some very recent research hints that plants may respond to sounds. Not to music mind you, which is irrelevant for a plant, but to certain vibrations. It will be very interesting to see how this pans out.

On communication: 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. [And] a very recent study showed that plants also communicate through signals passed from root to root. In this case the “talking” plant had been stressed by drought, and it “told” its neighboring plants to prepare for a lack of water. We know the signal went through the roots because this never happened if the two plants were simply in neighboring pots. They had to have neighboring roots.

On memory: They have short term memory, immune memory and even trans-generational memory. [As an example of short term memory], 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.

Do they think? 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.

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. 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.

Read the full interview here. Daniel Chamovitz’s website is here. And his book, What a Plant Knows, is here. (While the book certainly communicates, it doesn’t, at least to the best of our knowledge, have its own sense of smell and hearing.)