Plant Families Join Forces to Fight Foes, Study Finds

October 01, 2012 - News Release

Cheaters never prosper – even in the plant world.

In a new study, researchers including a University of Guelph ecologist have found evidence that groups of plants benefit from sharing resources with their relatives and may even discourage “cheating” by freeloading strangers.

This study is the first to show effects of plant relatedness on beneficial partnerships with fungi that most plants rely on for growth and survival, says Prof. Hafiz Maherali, Department of Integrative Biology.

The research may ultimately help farmers looking to grow more crops more economically and with less environmental damage from synthetic fertilizers.

The study was published in the Proceedings of the Library of Sciences (PLoS) One by McMaster University biologists Amanda File and Susan Dudley, Maherali and John Klironomos at the University of British Columbia.

About nine in 10 plant species – from trees and grasses to crops and garden plants – depend on root fungi for water and nutrients, especially phosphorus and nitrogen. In return, fungi obtain sugars from plants in this mycorrhizal partnership on and around roots.

In this open network, individual plants might be “tempted” to cheat by gaining resources without offering sugars in return. The researchers wanted to see whether kin selection based on shared genes might encourage closely related plants to work together and discourage cheating.

In earlier research, Dudley was the first researcher to show that plants can distinguish between kin and “strangers” through root interactions, perhaps using chemical cues. For many organisms, kin recognition may evolve as individuals act more altruistically toward relatives sharing their DNA than toward strangers.

For this new study, the researchers grew groups of related and unrelated ragweed plants. They added a common species of mycorrhizal fungus and measured how much fungus grew in each group.

The fungal network was bigger in groups of sibling plants than in solitary plants and much larger than in “stranger” plants.

Related plants appear to contribute more sugars to their associated fungi than do unrelated plants and get more nutrient benefits, said Maherali. “We have shown that groups of kin support a larger fungal network, and this helps them obtain more nitrogen from soil.”

Their study also suggests that plants have found a way to prevent cheating among freeloaders while using a common fungal resource, although Maherali says that conclusion is still speculative: “Individuals grown with strangers provide fewer sugars, perhaps to prevent their neighbours from cheating.”

He says more research is needed to test that idea, perhaps by tracking sugar and nutrient flows more closely.

Maherali said the idea of plants and fungi co-operating and working to thwart cheaters may appear odd. But such behaviours might have evolved in a range of organisms – including plants and animals– as with any other survival strategy.

In turn, they might benefit human survival.

Farmers might use plant-fungi mutualism to naturally promote nutrient-boosting fungi and reduce the economic and environmental costs of fertilizing crops such as corn and soybeans, he said. “Many companies culture fungus to sell to gardeners and farmers for promoting plant growth.”

Prof. Hafiz Maherali
Department of Integrative Biology
519 824-4120, Ext. 52767 or 56014

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