Plant-fungal symbiosis

RESEARCHERS EXAMINING plants growing in the geothermal soils of Yellowstone National Park and Lassen Volcanic National Park have found evidence of symbiosis between fungi and plants that may hold clues to how plants adapt to and tolerate extreme environments. The research was published in the journal Science.

Biologists Regina Redman of the University of Washington and Joan Henson of Montana State University and their colleagues examined 200 samples of Dichanthelium lanuginosum, also called "Geyser's Dichanthelium," for fungal colonisation. They found what may be a new species of the fungus Curvularia that survives only in temperatures greater than 98 degrees when it associates with plants.

The researchers suggest that thermotolerance may occur through symbiotic mechanisms like heat dissipation by pigment, such as melanin, or activation of a `biological trigger' that tells the plant to react to temperature changes or strongly than plants that lack the fungus.

The researchers grew sample plants with and without the symbiotic fungus in a laboratory and heated the soil to test thermal resistance. The plants without the fungus shrivelled at 122 degrees, whereas those plants with the fungus tolerated the heat for three days. Plants were also subjected to intermittent temperatures of about 149 degrees. Fungus-free plants died, but the fungus-bearing plants survived for 10 days.

The researchers also demonstrated that the plants provide thermal protection to the fungus by isolating it in plant roots that had a field soil temperature of 113 degrees.

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