What a Plant Knows: A Field Guide to the Senses
by Daniel Chamovitz
Humans commonly anthropomorphize non-humans. It just seems easier, for example, to say that a plant “likes” a particular type of soil, even though we know that a plant doesn’t “like” anything because a plant does not experience emotion. What we really mean to say is that a plant is adapted to and therefore performs best in a particular type of soil. However, knowing this, is it plausible at all to say that a plant can see, smell, feel, hear, sense its location, or remember things? Daniel Chamovitz argues that it is, and he has plenty of credible research to support his thesis.
In short, plants have senses very similar to human senses and are far more aware than we might initially think. To be clear though, Chamovitz states early on in his book that his “use of the word ‘know’ is unorthodox. Plants don’t have a central nervous system; a plant doesn’t have a brain that coordinates information for its entire body.” Nor do they have noses or ears or eyes. Instead, when Chamovitz uses words like “see,” “smell,” “hear,” and “know,” he is referring to various chemical reactions and physiological phenomena that occur in plants which produce reactions that are analogous to human senses. When a willow tree is damaged by tent caterpillars, a neighboring willow tree becomes unpalatable to the caterpillars and thereby resists a similar fate. Why? Because the damaged willow tree releases a gaseous substance that nearby willow trees can sense (or “smell”). This is a signal for them to protect themselves by building up toxic chemicals in their leaves.
Another example offered by Chamovitz involves the ability of some plants to remember winter. Cherry blossoms appear in the spring because winter has passed. A certain period of cold temperatures is what induces this response. If the trees bloom too early, the blossoms will freeze. If they bloom too late, the fruits would not have time to mature before cold temperatures returned. The seeds of winter wheat are planted in the fall and germinate in the spring. They also require a period of cold temperatures in order to germinate. This process is called vernalization, and it involves a specific gene in the plant called flowering locus C (FLC). After vernalization, this gene is turned off which signals the plant to flower (provided that other environmental conditions, such as light and soil temperature, are conducive to flowering, etc.).
A common myth is that plants grow better when people say nice things to them or play relaxing music for them. Chamovitz thoroughly debunks this myth and concludes that no evidence has been found for plants being able to hear. Plants do however possess many of the same genes that humans possess, including several genes that when not functioning properly can result in deafness in humans. These genes encode proteins called myosins. Myosins in humans help form the hair cells in our inner ears which are essential for hearing. Myosins in plants help form root hairs which are essential for absorbing water from the soil. While the functions of these proteins are quite different in humans and plants, mutations in the genes code for these proteins can have drastic results for both.
All this talk about chemistry, genetics, and physiology may sound a bit intimidating…but don’t worry. While Chamovitz endeavours to tell the science accurately and in detail, he does so in a very approachable manner, making this an easy read for anyone with a basic understanding of biology. Even if you don’t fully comprehend the technical stuff, the anecdotes are well told and captivating, and after you finish reading this, you are certain to have a greater appreciation for plants and all of the fascinating things that they can do. While we should be careful to be too anthropocentric, this book makes it clear that plants are a lot like us…or should I say, we are a lot like plants? Either way, we have many things in common (including much of our DNA), which is all the more reason to appreciate plants for the amazing organisms that they are.
This is a video (recommended by Chamovitz) of a dodder plant sensing the location of a tomato plant. Dodder is unable to photosynthesize, so after attaching itself to the tomato plant it will feed on the nutrients that the tomato plant produces.