Why folk who find plants dim are the real vegetables

ANOTHER LIFE:ONCE AGAIN I planted the garlic late, kneeling on a frosty morning to push a dozen rows of cloves into the soil. That sounds more penitential than it was – the snowy mountain gleamed beautifully in the sun – but garlic is best planted in November, with a month or two of winter chill to prompt the little root-buds that make multiple cloves for the growing bulb in spring.

Spain grows its best garlic over winter on the bleak plateau of La Mancha, Don Quixote’s country, and France’s garlic heartland is high on the Massif Central. For February planting, even in a winter like this, one relies on commercial lowland juggling with cultivars and cold stores.

The growth of plants is a lot more complicated, sensitive – even intelligent – than their sedentary lifestyle may suggest, and while the word “evolution” more commonly brings the animal world to mind, plant structures and behaviour have a place in it, too. This is the year to remember Charles Darwin at home, his study crowded with growing plants: runner beans, cucumbers, nasturtiums, clematis, hops, tropical vines – anything that climbed and thus moved with some apparent volition.

I have written here of the awe one can feel when a young pea-plant reaches out for a supporting twig and wraps its tendril around it – how did it know it was there? Without today’s time-lapse photography, Darwin and his son Francis had to watch patiently to decide, first, that climbers cast about with a tip or tendril, like a man swinging a rope around his head. They went on to work out that the tendril whips around the twig (in very slow motion) by a differential growth of cells: those touching the twig stop growing, while those on the outside of the tendril elongate, pushing it around in a spiral. The same search-and-spiral movement – the Darwins called it “circumnutation” – works for climbers twirling up poles.

This prompted scientists to speculate on plant “intelligence”.

As Francis Darwin said in a Dublin address to the British Association for the Advancement of Science (of which he was president): “We must believe that in plants there exists a faint copy of what we know as consciousness in ourselves.” The New York Times reported this (on February 28th, 1909) under the heading “Dr Francis Darwin’s Theory of Plant Intelligence Divides Botanists Into Rival Camps”. Today, the nature and degree of the intelligence can still be controversial, but a whole community of scientists feel comfortable exploring “plant neurobiology”, under which umbrella they will confer again in Florence in May. The newly coined term mainly covers the physiological basis of adaptive behaviour in plants, but it also extends to plant signalling, and communication, memory and learning.

A prominent spokesman for such faculties is Prof Anthony Trevawas of Edinburgh University. Failure to appreciate the intelligent plant, he suggests, has arisen from the different time scales of plant and human movement (the time-lapse camera has been revelatory), and plants’ rootedness in one place. When a plant can adapt its shape, plasticity and behaviour individually, according to environment, in foraging for food undergound and maximising access to light, it is showing more than reflex action. It uses chemicals and hormones for communication, rather than nerves, as animals do, with the main signals coming from control-points at the tips of shoots, the meristems. (Charles Darwin discovered that, by cutting off a shoot-tip, he could stop it bending towards the light.)

In animal laboratories, intelligent behaviour is judged by the capacity to navigate a maze for a reward. Yet, plants’ individual branches that navigate complicated gaps to reach the light get no such recognition. “To any wild plant,” writes Trevawas, “the environment represents a continual maze.” Research suggests that plants can anticipate environmental changes, even beyond trees dropping their leaves ahead of winter.

Sensing far-red radiation from a neighbour’s leaves, for example, plants will grow away from impending shade even before it happens. They seem to have memory: primed by an initial insect attack, they respond better and faster to a second one, or produce offspring less prone to being eaten. They can “communicate”, emitting volatile chemicals that attract predators and parasites of the insects damaging them, or cause neighbouring plants to mobilise their chemical defences.

All this might go down well with people who feel for plants, as it were, and try to treat them well. But Dr Trevawas and Prince Charles, as it happens, would have little to say to each other. The professor declares that remaining wilderness and biodiversity can only be protected by raising yields from existing farmland with GM crops, and never mind this organic growing nonsense.

They say a garlic garland wards off such evil spirits . . .

• Ireland's Ocean : A Natural History by Michael Viney and Ethna Viney has now been published by The Collins Press, Cork, €29.95

EYE ON NATURE

What is the evolutionary advantage in swans mating for life?

Linda Keohane, Furbo, Co Galway.

As swans spend two to three weeks egg-laying, 35 days on incubation and four-five months looking after the young, extra time and energy needed to attract a mate would minimise their reproductive time and threaten cygnets’ survival.

My daughter and her partner rescued a cormorant that had a wound at the base of its spine. The vet gave it antibiotics and it ate sardines. After a week it let them stroke it. When it could flap its wings they brought it to the pier and let it go. Watching it swim away and dive was pleasure beyond words.

Geraldine Furlong, Kilkee, Co Clare.

A treecreeper that normally climbs on birches and hawthorn has taken to feeding on peanut crumbs on the ground under the feeders.

Kieran FitzPatrick, Greystones, Co Dublin.

Treecreepers eat insects. This one is probably finding some among the crumbs.

During the snow, under an old Bramley apple tree, I counted 34 fieldfares, 13 blackbirds (two hens) and three hen chaffinches. Later I counted 97 fieldfares and blackbirds.

Michael McCarthy, Carlow.

Michael Viney welcomes observations at Thallabawn, Carrowniskey PO, Westport, Co Mayo. E-mail: viney@anu.ie. Include a postal address.