The underground communication of plants

In our last feature we reported on the communication system of trees.

“Secrets of the forest – a study proves that the forest has a positive influence on our health!” But it is not only trees that communicate with one another – other plants do too.

Swedish agricultural scientists have now discovered that maize seedlings growing close together send out signals underground via their roots that influence the growth of neighbouring plants.

The plants are said to use a complex system of chemical communication with which they can compensate for their inability to move, explained researchers led by Ali Elhakeem and Velemir Ninkovic of the Swedish University of Agricultural Sciences in the current issue of the journal “PLoS ONE”.

Plants often release chemical secretions into the soil through their roots, which neighbouring plants can then detect. The other plants draw information from them – for example, whether their neighbour is a related or an unrelated variety. This in turn influences their growth. The researchers wanted to understand even better how plants communicate with one another, so they touched the leaves of maize seedlings. In this way they simulated plants growing in close proximity that occasionally touch each other. The chemical solutions the plants then released through their roots were analysed.

The result was clear: plants newly exposed to these growth chemicals reacted immediately by devoting their resources to producing more leaves, while developing fewer roots than the plants in a control group.

Newly germinated maize plants were also studied. The aim was to find out whether there were differences between the growth chemicals of the touched plants and those of plants that had not been stressed.

Here, too, the result was clear: near unstressed plants, the new seedlings preferentially grew roots in their direction. This led the researchers to conclude that the plants are quite capable of distinguishing between the two kinds of secretion.

The experiments showed that even plants that were only briefly touched above ground responded by changing their secretions below ground in such a way that their neighbours changed their growth strategies accordingly.

These experiments show that changes caused by above-ground mechanical touch stress serve, through underground chemical interaction between plants, as a kind of forecast of future competitors for resources.

FURTHER READING Follow the links for more in-depth reading and to our last feature, “Secrets of the forest”.

PLoS ONE SECRETS OF THE FOREST