ANOTHER LIFE/Michael Viney: Stooped above the bench in the greenhouse, I hold a tiny tomato-plant seedling by one of its first two leaves and lower its hair-fine tendril of a root into the hole I have dibbed with my finger.
I want the root to hang all the way down in the hole before pressing the compost around it, but it keeps jerking around, trying to cleave to the side of the hole as if attracted by some magnetic or electrical force.
Perhaps science has a cause for this; perhaps my aim isn't as good as it was. Each spring I welcome the phenomenon without trying very hard to solve it - what is a rite without a bit of mystery? In the living room, I am training a vine up a string and round the ceiling. A tendril is reaching out to grasp the string from inches away; how does it know it is there? The books say that plants make wide, sweeping movements in slow motion until their tendrils connect with something, then whip around it fast, steering the movement by differential cellular growth-rates. I think our vine knows quite well where it's going.
Plants certainly move in many other ways than up, and what seems, for example, a bramble's "blind" groping for a new roothold on the far side of the ditch may be more than a programmed extension of growth. Plants can even seem to show foresight, one of the criteria human beings insist on in any demonstration of "intelligence".
Botanists have known for decades, for example, that growing shoots can sense the presence of nearby vegetation; green leaves absorb red light but reflect infra-red (hence the silvery look of foliage photographed with an infra-red filter). Plants, it seems, can measure the change in the light - and then make plans which take this into account.
According to Professor Anthony Trevawas, a molecular biologist at Edinburgh University, a plant that senses the growth of close neighbours will alter the structure of leaves and stems to secure its future share of sunlight. This kind of behavioural adaptation fits at least some definitions of intelligence and even implies an individuality; no two plants - even genetic clones - turn out identically, even in apparently identical laboratory conditions. But the real subtleties, holds Trevawas, can only be explored where plants are growing in the wild, in infinitely variable environments.
More than a century ago, Charles Darwin noted that: "Light seems to act on plants in nearly the same manner as it does on animals by means of the nervous system." Today we know that plants respond to some 15 different sensory signals, many tactile, electrical and chemical cues among them, and molecular biologists like Trevawas are finding strong similarities between the nervous systems of animals and the chemical signalling systems of plants. Both systems, for example, use calcium ions in passing messages internally and computing the significance of signals.
The plants' responses add up to what Trevawas calls a "mindless mastery" of their environment; he nowhere suggests a plant "brain". Back in 1970, Soviet scientists in the Agricultural Academy of Moscow were reported as proposing that plants had a recollection centre at the "root neck" that pulsated like an animal heart. Recordings of tiny electrical pulses were equated in Pravda and elsewhere with plant voices and shrieks.
This research took its place in a positive festival of international experiment, amateur and professional, and often of dubious scientific rigour, which claimed to demonstrate plant telepathy and emotions. An American polygraph expert, linking plants to his machine, found them happy at being watered, worried when dogs came near and apt to "faint" at the threat of violence.
Other work seemed to confirm the conviction of many gardeners (Prince Charles and myself among them) that plants respond to being talked to with affection, or given the odd caress. The gardeners of Findhorn, full of New Age spirituality, coaxed gigantic cabbages from near-barren Scottish sand.
My habit of treating my vegetables to afternoon sessions of Lyric FM's Full Score while I am working, chimes well with Indian experiments of broadcasting music to rice crops to increase the yield; quite literally, it gives out the right vibes.
When some plants - acacias, for example - are attacked by pests, they send out chemical signals to alert neighbouring acacias to secrete a foul-tasting defence. Sweet corn attacked by a particular caterpillar is able to identify it and send out signals to attract the right kind of predatory wasp. Such findings merely hint at the astonishing complexity and subtlety of what remains to be discovered about the secret and unexpectedly complex life of plants. By comparison, the intrusions of genetic engineering seem as subtle as an axe.