The green network

Somewhere in Canada, a little maple plant is under attack. It’s attackers are the greenflies, also called plant lice. The insects have bitten into the maple’s stem and are drinking the sap, it’s life juice. There is not much the plant can do for itself. But already, it has started sending signals that are going to save many of its friends around.

The signals are molecules of certain chemicals. They will reach the plants around the one that is under attack. As soon as the surrounding plants receive the signals, they will start preparing their defense. They will emit chemicals that will repel the greenflies. They also have in stock scents that attract wasps who eat the greenflies. The plants even know a method to make an insecticide. All these defenses are going to come handy against the attackers. Even though some little maples will be damaged, many are going to survive the attack.

No, this is not a science fiction tale. Researchers have found that plants actually communicate and alert each other of dangers like attack of herbivores, the plant eaters. They do so with the help of chemicals called volatile organic compounds, or VOC. VOCs are nothing but chemicals that can produce smells, like the perfumes that we use.

These signals are transmitted between plants in two ways – one is through air as we have seen. Another is through the soil. The roots of plants are in touch with each other, through which the chemical signals travel. But there is another interesting network under soil.

Some types of fungi make long threads that connect the roots of various trees and plants, making a vast underground network. The fungi get sugar from the roots, and give nutrients like nitrogen and phosphorous. This network is used to carry the plant messages too.

To ignorant observers like us, the plants appear to be just sitting quietly. Only now we are beginning to understand that they have a solid social network to exchange gossip, rumors and news. Remember that next time you pluck a casual flower from the bush.