Thursday, April 10, 2014

The Thought Life of Plants, Worms & Jelly-Fish

Non-Human Senses

Plant Sensitivity: The article says: "The Large Flowering Sensitive Plant, whose ‘plant electricity,’ Oliver Sacks writes, ‘moves slowly…as one can see by watching the leaflets…closing one by one along a leaf that is touched.’ 
Credit: Illustration from Robert John Thornton’s The Temple of Flora (1799–1807); published in a new edition by Taschen.Source: NYRB
In a book review article in The New York Review of Books, Oliver Sacks discusses whether plants, worms and jelly-fish, among many other so-called lower forms, have some sort of mental life. Sacks, the well-known neurologist and writer, reviews a number of books that have examined the issue.

Sacks starts off with Darwin's last book on the earthworm, a lowly creature, and writes:
Charles Darwin’s last book, published in 1881, was a study of the humble earthworm. His main theme—expressed in the title, The Formation of Vegetable Mould through the Action of Worms—was the immense power of worms, in vast numbers and over millions of years, to till the soil and change the face of the earth. But his opening chapters are devoted more simply to the “habits” of worms.
Worms can distinguish between light and dark, and they generally stay underground, safe from predators, during daylight hours. They have no ears, but if they are deaf to aerial vibration, they are exceedingly sensitive to vibrations conducted through the earth, as might be generated by the footsteps of approaching animals. All of these sensations, Darwin noted, are transmitted to collections of nerve cells (he called them “the cerebral ganglia”) in the worm’s head.
“When a worm is suddenly illuminated,” Darwin wrote, it “dashes like a rabbit into its burrow.” He noted that he was “at first led to look at the action as a reflex one,” but then observed that this behavior could be modified—for instance, when a worm was otherwise engaged, it showed no withdrawal with sudden exposure to light.
For Darwin, the ability to modulate responses indicated “the presence of a mind of some kind.” He also wrote of the “mental qualities” of worms in relation to their plugging up their burrows, noting that “if worms are able to judge…having drawn an object close to the mouths of their burrows, how best to drag it in, they must acquire some notion of its general shape.” This moved him to argue that worms “deserve to be called intelligent, for they then act in nearly the same manner as a man under similar circumstances.”
I have not read any of the other works cited in this essay,which I hope to soon rectify, but even so Sacks article has got me thinking about the nature of plants as we humans can understand them. I have a number of plants in our two-bedroom apartment, and all are doing well, having survived a couple of moves, including one to another city. Such shows their heartiness no doubt; I sense that plants can also tune in to whether they are liked and appreciated.

This might unnerve some scientifically minded individuals, but plants, I sense, do enjoy music and human communication. Plants thrive in positive environments, an argument that no one would find objectionable. They provide something important to humans, including visual beauty and inducing a sense of well-being or harmony.

But do plants think? Well, they do in their particular way, Sacks says:
Plants depend largely on calcium ion channels, which suit their relatively slow lives perfectly. As Daniel Chamovitz argues in his book What a Plant Knows (2012), plants are capable of registering what we would call sights, sounds, tactile signals, and much more. Plants know what to do, and they “remember.” But without neurons, plants do not learn in the same way that animals do; instead they rely on a vast arsenal of different chemicals and what Darwin termed “devices.” The blueprints for these must all be encoded in the plant’s genome, and indeed plant genomes are often larger than our own.
That some plants have a larger genome than humans is fascinating in itself; that plants can learn in ways that differ than humans is equally fascinating.

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You can read more at [NYRB]

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