But I think we also have to ask the question of intent (if we can even use that word when describing plants, but humor me while I anthropomorphize). Are the trees communicating, meaning is that attacked tree warning its surrounding ones? Or could it be more subtle? Maybe it makes more sense that the attacked branch is communicating to the other branches of the same tree in an effort for self survival, while the neighboring trees, well they’re just eavesdropping and benefiting from the signal.
There are also other examples of this type of communication. For example 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.
5. 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 transgenerational memory! I know this is a hard concept to grasp for some people, but 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. 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.
6. 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.
7. 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.