Technology & Science

Plants cheat on, exploit fungal relationships

Some plants take advantage of fungi lacking fruiting bodies to obtain nutrients without offering sugars in return.

Scientists thought green plants absorbed minerals with the help of soil fungi that gained sugars in exchange. But the relationship isn't always as mutually beneficial as it seems.

Some plants cheat, researchers have found. The plants use fungi, called mycorrhizae, as a bridge to access nutrients. Mycorrhizae come in two types: ectomycorrhizae and arbuscular.

Ectomycorrhizae such as edible chanterelle mushrooms and truffles are known to take fungal victims.

No one had ever observed the cheating relationship in arbuscular mycorrhizae (AM), though. Their hidden, underground life and lack of fruiting bodies tended to obscure them from scientists' prying microscopes.

Now researchers at the University of California, Berkeley have used molecular tools to identify how AM relationships have been taken for a ride by plants.

About 400 species of otherwise green plants have lost their ability to make sugars through photosynthesis and rely on fungi. The arbuscular/plant associations make up 70 per cent of all plants species, including those of many agricultural crops.

Plant biologist Martin Bidartondo and his colleagues found the arbuscular associations are highly specific.

Their findings, which appear in this week's issue of the journal Nature, are supported by greenhouse studies that found a single fungal species can form AM relationships with many different plant species.

In a commentary that accompanies the study, biologist David Hibbett of Clark University in Worchester, Mass., said Bidartondo's findings are significant.

The study shows "mutualisms are not stable endpoints in evolution, but are inherently unstable and can be disrupted by conflicts of interest among the partners."