Visions and Insights in Biology: Electrical Signaling and Counting in Plants

A colleague of mine, a plant physiologist and biochemist, a member of the National Academy of Sciences, was a professor at Cornell, a connoisseur of music and art, and an amateur violinist. The Cornell campus sits on a hill overlooking downtown Ithaca (New York). My colleague told a story many years ago about giving a ride back to campus to a female student. They fell into conversation and the student learned that he worked on plants, whereupon she began to talk about how she thought that plants might appreciate music. After listening to a few sentences in this vein, he could not contain himself: “That is a crock.” This was the closest we ever got to hearing of any manifestation of irritation on his part to anyone; so clearly he was definitely not sympathetic to the idea that plants were sentient.

Plants do not have brains; they depend heavily on their complex biochemistry and their fecundity to survive the vicissitudes of the environment. But it is fair to ask what sort of a nervous system a plant might have. It turns out that it is not zero. One of my favorite videos to show students is here.  The video shows a venus fly trap (much appreciated by Darwin himself) capturing an insect. The video goes on to describe how action potentials are coupled to the stimulation of the hairs on the upward-facing surface of the leafy green trap. These action potentials look like those that function in the neurons of animals! As shown by Böhm and colleagues in a recent issue of Current Biology, the plant appears to be able to count the action potentials and discriminate against single stimulations, requiring at least two action potentials within 10 – 15 seconds before closing the trap on the unfortunate insect.

venusflytrap
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Further struggling by the insect produces additional action potentials, which activate a battery of genes concerned with digesting the insect and harvesting its nutrients. Thus, the plant seems to be able to count beyond two. That is a smart plant! Action potentials are found in other plants, and plants can respond to tactile signals, for example vines, or other carnivorous plant species.  Certain flowers “shoot” pollen at bees that buzz in a specific manner. The model plant Arabidopsis can perceive the sound of caterpillars feeding and respond by producing oils that repel them. So far as I know, however, there is no evidence that plants can appreciate music.

 

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