The plants kept in dry conditions responded to the situation by closing the pores on their leaves (which are called stoma) – a normal reaction for plants in drought. What was unexpected was that plants nearby (not kept in drought conditions but sharing the same soil) did the same thing! Not only that, but they seemed to pass the message on to un-stressed plants even further away, which responded with stomatal closure as well. The plants that did not share any soil did not respond at all, meaning that the communication between the plants was done through root systems rather than the leaves.
According to Professor Ariel Novoplansky who oversaw the research, “The results demonstrate that unstressed plants are able to perceive and respond to stress cues emitted by the roots of their drought-stressed neighbors and, via ‘relay cuing’, elicit stress responses in further unstressed plants. Further work is underway to study the underlying mechanisms of this new mode of plant communication and its possible adaptive implications for the anticipation of forthcoming abiotic stresses by plants.”
Previous research by Exeter University in Britain also turned up evidence of plant communication. In that study, cabbages were used rather than pea plants and the form of communication was quite different. In this case, the cabbages were also placed close to each other. Certain cabbages had their leaves snipped with scissors. This caused the damaged plants to emit a gas, made visible through genetic mutation, which alerted their neighbours. The nearby cabbages reacted to this gas by producing a toxin in their leaves making them less palatable to predators such as caterpillars.
Iain Stewart, a professor of Geoscience Communication who witnessed the experiment at Exeter University, commented: “It’s fascinating to realise that there could be a constant chatter going on between different plants, that they can in some way sense chemically what is happening to others, like a hidden language which could be going on all around us. Most people assume that plants lead a rather passive life, but in reality they move and sense and communicate. It’s almost like they show a kind of intelligence.” Fascinating indeed!