Can Plants Feel?

In the latest in his series on intelligent plants, Martyn Baguley assesses whether plants have the ability to feel

Martyn Baguley

I used to take groups of post-graduate landscape architecture students on ecology field trips. With their minds on higher planes like landscape design and lines of vision, most weren’t particularly interested in soil types and associated vegetation, until I took them to a piece of acid moorland, drew their attention to a small plant nestling amongst heather and told them it was carnivorous. ‘Higher planes’ were instantly forgotten and the students would cluster round, swat flies and drop them onto the diminutive plant to see what it did. Was that an expression of our baser instincts?

The plant was a sundew (Drosera rotundifolia – ‘Drosera’ from the Greek word droseros meaning ‘dewy’, from the appearance of glistening hairs on the leaves; ‘rotundifolia’ meaning round-leaved). Sundews have tentacles on their leaves with glandular heads that produce a sticky mucilage that reflects light and attracts insects. Once on the leaves the insects, stuck by the mucilage, struggle to escape, which results in them becoming more covered in the mucilage. In no more than ten seconds their struggles stimulate the plant’s tentacles to bend inwards and the leaves to curl up, trapping the insects which are suffocated. The whole process takes about three minutes. Enzymes are then produced by the plant from glands and the insects are eventually digested. So there you have it – grisly, unquestionable evidence of one genus of plants ‘feeling’ the dying struggles of their insect prey.

Carnivorous plants are adapted to growing in places where soils are deficient, particularly in nitrogen, like acidic bogs, compensating for the deficiencies by trapping and digesting animal life. There are estimated to be some 200 species of Drosera worldwide (only one in Derbyshire – Round-leaved Sundew plants are rare, but they can be found in areas of wet peat and sphagnum moss in the moorlands of the Dark Peak) and at least 583 other carnivorous plant species that attract, trap and kill prey, many of which deploy the sense of touch in the process. The biggest is a pitcher plant, Nepenthes raja, which grows in Malaysia and is said to be capable of trapping and digesting small mammals.