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Distress Signals the Leafy Way

By Saakshi Khanna; Illustration by Kusum Chamoli

Wondered how plants talk to each other? They do not have the same language as humans but they have their own ways. Recent research by scientists at Kyoto University, Japan, describes how the Lima bean plant protects itself and its neighbours from the spider mite or the red spider. It sends out clear distress signals. Its not like they make weird noises to attract attention, though. It does it very silently.

The Lima bean plant emits chemicals to send the message of a troublesome intruder to all its neighbours. That is the signal for all the plants to get their defense mechanisms working.

Plants all over the world have qualities, which make then special in their own ways. Some plants produce chemicals that give the leaves and stem a strong taste or smell of chillies, spices and herbs used for cooking. These substances either discourage or even kill insects and other animals that might try to eat the plant.

Since plants cannot escape from creatures that feed on them, many have evolved features to protect them against herbivorous or plant eating animals. The two main defenses that plants use are armour and poison. In the Galapagos Islands cacti grow a thick stalk more than two metres tall putting the tender leaves well out of the reach of the giant tortoises.

Japnese azaleas produce toxic chemicals that let them survive even among hungry deer. Some of these chemical substances may even prevent the growth of nearby plants. For example, radishes produce a chemical substance, which slows the growth of spinach Similarly, walnut and apple trees cannot grow together because chemicals released from walnut tree kill the apple tree.

So it is not just a self-survival instinct that plants have. They also have an instinct for community feeling, as the Lima bean plant shows. Nature is full of unending surprises!