It was while investigating the genes responsible for regulating plants’ responses to light and dark that Daniel Chamovitz, a research biologist, became interested in the parallels between plant and human biology. How do plants ‘know’ that they must turn towards light, and how does this correspond with human responses to light? And if a plant can ‘see’ (that is detect difference in shades of light and darkness) can it also feel, hear, smell, or retain memories? What A Plant Knows is the wonderful result of Chamovitz’s research into these questions, and without giving too much away, it turns out that most of these senses are felt by plants just as much as humans.
But it is only by broadening our notions of what it is to see, feel or remember that we can justly apply these characteristics to plants, and throughout this book we are invited to perform interesting thought experiments about what exactly it means to smell or remember or hear, at both simple and complex levels. Chamovitz is at pains to point out that while plants can detect a range of sensations in ways very similar to humans, they do not have brains and so there is no reasoning or emotional component to what they ‘know’. For example, a plant can ‘know’ that its neighbour is being attacked by beetles by ‘smelling’ the chemicals released by the damaged leaves, and respond by producing its own defensive chemicals to deter beetle attack, but without a brain a plant cannot have an emotional response to its neighbour’s demise. Humans, on the other hand, not only take defensive action on learning of a neighbour’s injury or illness (‘She has cancer; I should really stop smoking,’ or ‘He hit his head falling from his bike; I’d better wear a helmet when I cycle’) but our practical responses are tied up with emotional ones: ‘Poor him, I do hope he wasn’t very hurt’ or, ‘I am worried about what will happen to her children.’ We can all too easily attribute such human emotions to other living things, and Chamovitz warns us against the silliness of anthropomorphising plants. With no brain to perform complex reasoning, your Camellia japonica cannot worry or fret any more than your dining table can. There is no need to wince when pruning a branch from your favourite tree. The tree knows that the branch has been removed, and will respond by healing the wound, but it cannot feel pain (a sensation useful only in creatures that can respond by moving away from a painful stimulus) and it certainly would not feel the ranges of anger, worry and grief that a human might feel on losing a limb. Plant responses are emotionless and practical, and if anything this book caused me to ponder on the energy that we humans expend in our sometimes crazy, overblown responses to adverse events.
There is one plant sense that Chamovitz fails to find any evidence for: suffice to say that when Prince Charles whispers sweet nothings to his dahlias, his words fall on deaf… leaves. But any disappointment the reader may feel over the stubborn inability of their plants to listen to, let alone ‘enjoy’, Mozart or The Beatles will be more than assuaged by Chamovitz’s astonishing and delightful chapter on plant memory.
The book is not without its small transgressions. I felt that the accurate word should not have been far from Chamovitz’s reach when without irony he stated that leaves ‘inhale’ molecules, a choice of verb that aptly demonstrates his subsequent point about our unwitting tendency to anthropomorphise plants. Chamovitz also overstrains himself in his first chapter to defend what I thought were perfectly reasonable comparisons of plants to humans, but he soon settles more comfortably into his theme and strings his arguments and ideas interestingly throughout this delightful and charming book, lending the scientist gardener a multitude of novel ideas and fresh perspectives of the minute and unnoticed goings-on among the plants in our gardens and beyond.
Chamovitz, D. (2012) What a Plant Knows. 4th edition, London: Oneworld Publications.