Why Don’t You Ask the Plant?

By Tristan Wang ’16, THURJ Staff

We’ve lived side by side with plants since our birth. Touching the grass during a game of football or listening to the trees whisper during the fall, we have been constantly interacting with plants. At some point, most of us have wondered what these living organisms think. How do they feel? Are they like us? Through human imagination, movies have portrayed plants as victims suffering the onslaught of lumberjacks in Lord of the Rings and apple-pickings in The Wizard of Oz. Daniel Chamovitz, author of What a Plant Knows, attempts to explain what the world looks, smells, and feels like through the perspective of plants.

To Chamovitz, plants are fascinating because their physiology is so closely related to that of animals. Certain senses and abilities of animals are shared with plants even though the latter group lead a much more sedentary life. In essence, plants “have evolved complex sensory and regulatory systems that allow them to modulate their growth in response to ever-changing conditions” and must “be able to withstand and adapt to constantly changing weather, encroaching neighbors, and invading pests without being able to move to a better environment” (4). By drawing comparisons between the ways in which plants and animals perceive the world, he challenges the fundamentals of what it truly means to see, smell and feel the world.

The Merriam-Webster Dictionary defines sight as “the physical sense by which light stimuli received by the eye are interpreted by the brain and constructed into a representation of the position shape, brightness, and usually color of objects in space” (10). Simply by removing the anatomical specifications of the eye and brain, this definition could apply to plants as well. As shown by a well-known experiment of Charles Darwin, canary grass bends towards the light, indicating the presence of a sensory mechanism. Even more interestingly, if the tip of the grass is trimmed off, the plant can no longer react to light, which reveals region specificity for this sense. In fact, one could easily argue that, compared to human sight, plant “vision” is just as elaborate—if not more. Phytochromes help to regulate circadian rhythms that control plant processes, and Arabidopsis alone has at least eleven distinct photoreceptors. To plants, light “is much more than a signal; light is food,” and it may be this importance of light that explains the complex system of utilizing and sensing light (22).

In addition, other senses can be explained by their utility to plants when understanding what it means to smell, taste, hear and feel. To smell is to detect odors through olfactory nerves, and to feel the world around us encompasses receptors for both pain and pressure. While plants obviously lack the nervous system to replicate animals’ sense of touch, is such an elaborate physiology necessary? Evidence for the influence of sound on plants is lacking, ostensibly because plants have no need for audible signals and vocalizations since they cannot physically escape from predators.

Throughout the book, Chamovitz applies research, both recent and historical, to further demonstrate the correlations between plant and animal behaviors. He skillfully uses many reputable experiments such as Darwin’s tip-removal of canary grass and Thomas Andrey Knight’s spinning wheel that explains gravity’s effects on the direction of plant growth. Moreover, he supplements these examples with many recent research projects to explain why plants act the way they do. For example, at Penn State University, Dr. Consuelo De Morales’s work with the parasitic dodder plant demonstrated that specific chemicals emitted by tomato plants make them a more attractive target for parasitism than other plants.

From all of these examples of plants reacting to environmental stimuli, Chamovitz did not intend to find “an argument that plants are just like us” but rather elaborate how sensory information is processed in plants in comparison to animals (5). The book emphasizes that, considering the similarities between the two kingdoms, we can understand more about ourselves by learning about how plants work. In the beginning of the book, Chamovitz was also surprised that the “unique group of genes necessary for a plant to determine if it’s in the light or in the dark…is also part of the human DNA” (3). While Chamovitz focuses more on the historical and current perspective on how both animals and plants utilize their senses, it opens the door for relevant discussion about genetics.

References

Chamovitz, Daniel. What a Plant Knows: A Field Guide to the Senses. New York: Scientific American/Farrar, Straus and Giroux, 2012. Print.

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