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News Release

June 10, 2004

Underground fungi influence plant growth, soil, environment, says prof

A type of fungus that lives below the soil has a huge influence on plant growth, the quality of soil and even the amount of carbon in the environment, says a University of Guelph professor.

“By missing out on all of the interactions between above- and below-ground organisms, we’re not getting the whole picture,” said botany professor John Klironomos, whose research will appear in the June 11 issue of Science. “When studying plants, the feedback from what happens below ground can’t be ignored.”

In their review paper for a special issue of Science dedicated to soils, Klironomos and five other researchers show that although soil organisms are rarely considered by ecologists, there are significant interactions between the organisms found below ground and those found above ground.

“Our lab is showing that rather than plants competing with each other, fungi are often facilitating one plant getting nutrients from another so they can co-exist,” said Klironomos. “So rather than competition among plants being the centre of plant ecology, it could be mutualism, which could change everything.”

Klironomos, a Tier 2 Canada Research Chair who has established an advanced soil ecology analysis lab and training centre at U of G, said a group of fungi – arbuscular mycorrhizal fungi – send out extensive fine threads only 1/10th to 1/100th the diameter of a plant root, which link up with the roots of most plants and extend their reach up to 20,000 kilometres in one cubic metre of soil. Their small size and ability to produce enzymes allow the threads to pick up nutrients and transfer them back to the plant. It’s a mutual exchange; in return for providing the plants with nutrients, the fungi receive sugars that they feed on from the plant.

Many plants can be linked to each other by these fungal threads, allowing nutrients to transfer not only from fungi to plant, but also from plant to plant. The roots of about 80 per cent of plants are entwined with mycorrhizal fungi. “If you were to carefully pick a plant up from the soil, you would actually see these tiny masses of fibres; they’re quite prominent,” said Klironomos.

Seeds and plants that can tap into this network have instant access to nutrients and a much higher chance of survival, he said. Since mycorrhizal fungi also hinder water loss and erosion, they improve the quality of soil.

Fungi influence much more than the plants they associate with. They play a large role in carbon storage, said Klironomos. With the concentration of CO2 increasing in the atmosphere 1˝ per cent every year, many people are looking to the ocean and the soil as possible places to store carbon, he said.

“Some species of mycorrhizal fungi can be huge carbon sinks. In some cases, only 15 per cent of the entire carbon budget is for the plant. The rest of it goes below ground. The mycorrhizal fungi can take up to 85 per cent of all the carbon produced by the plants for themselves.”

John Klironomos
Department of Botany
(250)762-5445, Ext. 7886, or

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