Plants can Recognize Their Siblings

Researchers at the University of Delaware have discovered that plants can recognize their siblings. The study was led by Harsh Bais, assistant professor of plant and soil sciences at the University of Delaware. The ID system of the plant is in the roots and the chemical cues they emanate. The discovery has implications for the future of agriculture and even home gardening.

In 2007 Susan Dudley, an evolutionary plant ecologist at McMaster University in Hamilton, Ontario, and her colleagues had observed that when siblings are grown next to each other in the soil, they “play nice” and don't send out more roots to compete with one another. In the contrary the moment one of the plants is thrown in with strangers, it begins competing with them by rapidly growing more roots to take up the water and mineral nutrients in the soil. Bais wanted to find the mechanism behind the sibling recognition and set up a study with wild populations of Arabidopsis thaliana.

Young seedlings were exposed to liquid media containing the root secretions or “exudates” from siblings, from strangers (non-siblings), or only their own exudates. The length of the longest lateral root and of the hypocotyl, the first leaf-like structure that forms on the plant, was measured. In one experiment, the root exudates were inhibited by sodium orthovanadate, which specifically blocks root secretions without imparting adverse growth effects on roots. The exposure of plants to the root exudates of strangers induced greater lateral root formation than exposure of plants to sibling exudates. Stranger recognition was abolished upon treatment with the secretion inhibitor.

Bais noted that Strangers planted next to each other are often shorter, as so much of their energy is directed at root growth. Siblings does not compete against each other and their roots are often much shallower. He also observed that sibling plants grow next to each other, their leaves often will touch and intertwine compared to strangers that grow rigidly upright and avoid touching.

Details of the research appear in the journal Communicative & Integrative Biology.