Sunflowers know to share

The natural world is sometimes portrayed as a vicious gladiatorial arena in which only the fittest, most selfish specimens survive. Not so for the sunflower – a study has shown that the plants co-operate below the surface, sharing nutrients and demonstrating the kind of collaborative behaviour once believed to be restricted to the animal kingdom.

The research looked at how the common sunflower deploys its roots to forage for sources of nutrition. Each plant has a main tap root off which smaller, hairy tributaries grow. A lone plant will send out more of these secondary roots when it encounters a patch of nutrientrich soil.

This behaviour changes when it has a neighbour that is as well placed to benefit from the same fertile patch. In such cases, each sunflower sends out fewer roots, as if they have agreed not to compete.

The paper, published yesterday in Proceedings of the Royal Society B, suggests that each plant is responding to its ‘‘social environment’’.

The paper joins a growing body of research hinting that no plant is an island. ‘‘We need to recognise that plants not only sense whether it’s light or dark or if they’ve been touched, but also whom they are interacting with,’’ said Susan Dudley, a plant evolutionary ecologist at Mcmaster University in Hamilton, Canada.

There is growing evidence trees can ‘‘talk’’ to each other through fungi. Research began in the 1990s when it was discovered fungi send out superfine threads known as hyphae that weave into tree roots. The system allows the roots of trees of different species to share resources and issue warnings about, for example, harmful parasites. – The Times