Are Plants Entering the Realm of the Sentient?

Astounding findings are emerging about plant awareness and intelligence.

Dr. Jagdish Chandra Bose
Source: “Jagadish Chandra Bose 1926” by Agence de presse Meurisse‏ – Bibliothèque nationale de France. Wikimedia Commons.

In the last couple of decades botany has begun to catch up with Bose’s ideas, leading scientists to some amazing questions: Are plants conscious? Do they have knowledge? Can they feel pain?

In 1992 researchers discovered that tomato plants will produce certain proteins throughout their bodies when they’re wounded. The speed of the response precludes the possibility of chemical signals; the plants are producing electrical signals to direct change to occur more quickly within more distant parts of the plant.

Slow yet Smart

We tend to look at plants as dumb and nearly inert. They’re anchored in place and seem to bend passively with the breeze and grow gradually to capture sunlight. With rare exceptions such as the Venus flytrap, they move only very slowly, such as when a vine seeks an object to attach to. With time-lapse photography, scientists have begun to capture plant movements that seem sensible and intelligent. Under time-lapse, the seedling of a Cuscuta (dodder) vine seems to search for a host by sniffing the air. It then lunges toward its new host when it finds one, resembling snake movements.

When plants seem to be behaving like animals, we must reconsider whether intelligence truly is an exclusively animal trait. Watch a Dodder vine sniff out its prey: http://video.pbs.org/viralplayer/2341198769

Scientists are indeed questioning whether this distinction is as clear-cut as modern science has previously assumed. In 2005 researchers founded the Society for Plant Neurobiology to advance this debate. A founder of the organization, the Italian scientist Stefano Mancuso, argues that we should stop assuming that a brain is needed for intelligence. Even without neurons and a brain, plants can acquire, process, and integrate information to shape their behavior in a way that could be called intelligent.

Locating Intelligence

As reported in a recent article in the magazine New Scientist,2 the apparent magic of consciousness in plants seems to depend on several physiological features, particularly those of their root systems. Plant roots include various “zones,” including a “transition zone,” which is electrically active and seems analogous to the animal brain—it contains a mechanism similar to neurotransmitters. Another part of the root, the root cap, can sense various physical properties “such as gravity, humidity, light, oxygen, and nutrients.”3 Most cells in plants can make and transmit neuron-like activity. In roots every cell can do so.

Mancuso says, “If we need to find an integrative processing part of the plant, we need to look at the roots.”4

Plants also produce serotonin, GABA, and melatonin, which act as hormones and neurotransmitters in animal brains, though it’s not yet known what they do in plants. Intriguingly, drugs such as Prozac, Ritalin, and methamphetamines can disrupt these “neurotransmitters” in plants.

Vital Capacities

Plants sense light, but they also communicate with one another using chemicals. They “know” when they’re being touched. They integrate all of this information without the kind of neural system that animals have.

And they have memory—the ability to store and recall an event at a later time. A Venus flytrap, for instance, doesn’t chomp down when it receives its first sensation of a fly; it only closes if the hairs in its trap sense another contact within a half minute or so. It “remembers” the first touch.

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