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.
More surprising is the result of an experiment that Mancuso carried out with Mimosa pudica, the “touch-me-not” plant. He and colleagues dropped potted mimosas repeatedly onto foam from 15 centimeters (about 6 inches) above. The plants closed their leaves in response to the fall initially, but stopped doing so after four to six drops. It seems that they “learned” that there was no danger. It’s not that they were no longer able to close their leaves—they still would do so in response to touch. They retained this ability to discriminate between the harmless fall and the potentially harmful (about to be eaten) touch after a month.
Consciousness?
Frantisek Baluska at the University of Bonn, Germany, has pushed further into the question of consciousness by suggesting that plants may even experience pain. They release the chemical ethylene when stressed—when being eaten, attacked, or cut. Nearby plants can sense the ethylene. One researcher equated this release of ethylene with a scream. Since plants also produce the chemical in large quantities when their fruit are ready to be eaten, there’s conjecture that they’re using ethylene as an anesthetic (animals can also be knocked out with ethylene, an anesthetic).
Psychologists and philosophers will likely debate the precise definition of intelligence until the end of time. It may in truth blend into the whole continuum of biological capacities—faculties of various kinds, particularly sensation and memory, that seem to exist throughout the animal world. But as we realize that plants have significant abilities in sensation, awareness, integration of information, long-term memory, and adaptive learning, we must at least leave open the possibility that intelligence is certainly not unique to humans and probably not even to animals.""
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