By Maneka Sanjay Gandhi

There is a fascinating book on the market “What a Plant Knows” by Daniel Chamowitz, 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 defence when under siege, and warn its neighbours of trouble on the way. A plant can even be said to have a memory.  Do plants think? Will future education classes include plant neurosciences in the curricula?

I think they should. Anyone who has played with the plant Chhooeemooee and watched the leaves close if they are touched and then open again when it thinks you are gone, knows that plants have senses and genes that regulate intelligence. Anyone who watches sunflowers turn to face the sun knows.

Chamowitz gave an interview on a site called Mind Matters. I am going to quote from it-

 “All of us know when it is day or night, all of us respond to light and dark. Do plants have the same response to light as animals? 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. It appeared these genes were unique to the plant kingdom But much to my surprise I later discovered that this same group of genes is also part of the human DNA. We now know that these same genes are important in animals for the timing of cell division, the growth of neurons, and the proper functioning of the immune system.”

“These genes also regulate responses to light in animals! Our internal 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. But fruit flies also go into jet lag if their clocks are changed. And so do plants. I realize that the genetic difference between plants and animals is not as significant as I had naively believed.”

Do plants have a sense of smell? “Of course. What is smell?  When we smell something, we sense a chemical that’s dissolved in the air, and then react. The clearest example in plants is what happens during fruit ripening. If you put a ripe and an unripe fruit together in the same bag, the unripe one will ripen faster. This happens because the ripe one releases a ripening pheromone into the air, and the green fruit smells it and then starts ripening itself. When one fruit starts to ripen, it releases this hormone which is called ethylene, which is sensed by neighboring fruits, until entire groves ripen in synchrony.”

“Another example of a plant using smell is how a parasitic plant called dodder finds its food. Dodder can’t do photosynthesis, and so has to live off 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.”

Can plants hear? “Many of us have heard stories about plants flourishing in rooms with classical music. From an evolutionary perspective, plants haven’t really needed to hear. Hearing in humans and other animals serves to warn of potentially dangerous situations. Hearing also enables rapid communication, enabling a rapid response which is often movement. But plants are rooted organisms. While they can grow toward the sun, and bend with gravity, they can’t flee. They can’t escape. They don’t migrate with the seasons. So, perhaps the audible signals we’re used to in our world are irrelevant for a plant. However, recent research shows that plants may respond to sounds and vibrations.” (Experiments at the Yoga Sciences Institute in Bangalore show that wheat grows faster and taller when exposed to shlokas).

Do plants communicate with each other? “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. This is definitely communication. A 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.”

Do plants have a memory? “Plants definitely have several different forms of memory, just like people do. They have short term memory, immune memory and even trans-generational memory. If memory entails forming the memory (encoding information), retaining the memory (storing information), and recalling the memory (retrieving information), then plants definitely remember. 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.  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 trans-generational memory that’s also been recently shown also in animals.”

Since the plant does not have a central brain, how does it do these things?  “Even in animals, not all information is processed or stored only in the brain. Different parts of the plant communicate with each other. 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, the entire plant is analogous to the brain.”

“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 the same drugs that inhibit the human glutamate receptor also affect plants communication from cell to cell. Darwin, one of the great plant researchers, proposed that the tip of the root, called the meristem, acts like the brain does in animals, receiving sensory input and directing movement.”

How do you think people should change in how they think about plants? “People have to realize that plants are complex organisms that live rich, sensual lives.  Many of us think of plants as inanimate objects, like stones.”

Think of this: Humans and animals can move to solve their problems. Thirsty? Get a drink. Lonely? Go to a party. Hot? Move to a cooler place. But a plant is rooted. It cannot escape. Therefore it needs to develop incredibly sensitive and complex senses to survive in changing environments. Plants need to see where their food is. They need to feel the weather, and they need to smell danger and then integrate this information. Start thinking of plants as sentient beings who share this planet with you. Behave better with them. From the grass you trample, to the cut flower you buy.

So much exciting research is going on. Fifty years from now, humans will look upon us as barbarians for having raped this planet in the belief that every animal and plant was a senseless object put merely for our pleasure. 

To join the animal welfare movement contact This email address is being protected from spambots. You need JavaScript enabled to view it., www.peopleforanimalsindia.org