Plant Brains or Nuthouse?

What outrageous idea led an esteemed Yale animal biologist to call his colleagues a “nuthouse”?

Plant intelligence. Michael Pollan at the New Yorker asks, do plants have it? Can plants “learn,” “solve problems,” and (most dangerously) “feel pain”?

The Highest Frontier imagines plants that solve problems (even problems beyond our own democracy) and people refusing to eat plants (Ken, the “microvore”). But what do real scientists think today?

As Pollan recounts, claims of plant intellect go back to Charles Darwin, in his less known book, The Power of Movement in Plants. Darwin argues that plant roots act like the “brain of a lower animal.” Plants could be upside-down animals, with their brain underground, and their sex organs (flowers) on top.

Nuthouse, say the animal scientists. Brains and neurons are for animals. And too many “plant life” experiments from the sixties turned out as bogus as ESP. But it’s been a long while since the sixties–and neuroscience, too has come a long way since ESP, let’s not forget. So today…where’s the experimental evidence?

• Plants integrate thousands of different chemical signals–using neurotransmitters such as serotonin, glutamate, even dopamine (the addiction in Brain Plague).
• Plants generate orders of magnitude more diverse biochemicals than animals do. They make psychoactive substances that intoxicate their grazers, or attract their pollinators.
• A plant root can “seek out” a buried pipe of flowing water. Do the roots “hear” the water’s sound?  A bean stalk somehow “detects” a distant pole, bending toward it to find and climb. Possibly echolocation?
• The Mimosa plant “folds up” at a touch, like the glowing plant in Avatar. But the Mimosa can “learn” not to bother, after repeated stimulation. And it “remembers” for days longer than insects do.

Could plants have a consciousness–yet live on a longer timescale, so long we cannot notice?

No one seems to ask yet whether plants can laugh. Perhaps their laughing at us already.