New research has shown that plants may be more intelligent than we think. A recent study conducted by the University of Western Australia, demonstrated that the plant, Mimosa pudica, could learn new behaviour and retain this memory for weeks. Mimosa pudica is a plant that when touched folds inwards, thought to be a reflex in response to predation. But when the plant was dropped several centimetres down repeatedly it quickly learnt, within minutes, that this posed no threat and stopped folding its leaves, a behaviour that persisted when plants were dropped weeks later. When shaken instead of dropped the plant would fold its leaves in response to this new threat. Watch a video of the plant’s response here.
Plant intelligence experiments are not new although earlier studies have been met with criticism for being unscientific. The 19773 book, “The Secret Life of Plants,” by Peter Tompkins and Christopher Bird, presented some of these, including experiments claiming plants could effectively read minds. Although much of this work has been discredited, it’s thought by some to have had a negative effect on the momentum of the field of plant intelligence. But this is changing. In 2006, an article in Trends in Plant Science suggested a new field called “plant neurobiology.” Authors of the article explained that some behaviour in plants could not be solely attributed to genetic and biochemical mechanisms but instead plants could sense and respond to a variety of factors: light, water, gravity, temperature, soil structure, nutrients, toxins, microbes, herbivores, chemical signals from other plants.
Of course plants don’t actually have brains but they do collect, analyse and integrate knowledge and react in new ways through analogous structures to our neurological system. They also don’t have ears but have been witnessed secreting defensive chemicals in response to hearing caterpillars eating nearby. Plants can also sense objects before coming into contact with them and move away from them. They have systems for sending electrical and chemical signals (such as dopamine or serotonin also found in humans). How these systems work is still largely unknown. And there remains significant disagreement, not least in calling the field plant neurobiology despite plants having no neurons, on the credibility of investigation into plant intelligence. In the 1980s scientists working on plant communication and signalling faced similar scorn. The Mimosa pudica experiment has also received its fair share of criticism with some scientists claiming the plant’s behaviour is more to do with habituation, desensitization or adaptation, talking issue with the use of the words learning, memory and intelligence.
So it seems plants can learn they can retain memory and they are conscious of their surroundings. Whether this can be called “intelligence” depends largely on the definition of intelligence but one thing is for sure, the differences between plants and animals is becoming much less clear.
More information can be found about plant intelligence and current debates by watching Stefano Mancuso’s TED talk.