Plants and fungi--growing together
Rodriguez, Rusty , Redman, Regina .
Symbiotic modulation: a mechanism for plant distribution patterns.
The geographical distribution of plants has been intensively studied for more than 275 years. Although much is known about plant distribution patterns across complex habitats, little is known about the mechanisms responsible for plant distribution patterns. Moreover, most plant studies do not consider the fact that all plants in natural ecosystems have symbiotic associations with fungi. We have found that plants growing in high-stress habitats have symbiotic associations with endophytic fungi that confer habitat-specific stress tolerance to plants. Therefore, endophytes from plants thriving in coastal beaches, geothermal soils and agricultural fields confer salt, heat and disease tolerance, respectively. Without the endophytes, plants that have "adapted" to specific habitats do not survive there. Recently, we found that plants growing across microhabitats which impose different selective pressures maximize fitness in each microhabitat by changing endophytic associations. For example, a native dunegrass growing from high salinity beach substrate up a slope of moderate soil salinity and onto low salinity meadow soils is symbiotic with three different fungal endophytes that are specific to the beach, slope, or meadow microhabitat. Laboratory studies indicated that the endophyte from plants on the: beach confer high levels of salt tolerance, slope confer moderate levels of salt tolerance, and meadow confer no salt tolerance. We have observed this phenomenon with several different plant species in coastal and geothermal habitats. In addition, endophytes are also able to change plant hosts in adjacent microhabitats that impose different selective pressures allowing for habitat expansion of fungal endophytes. We described this phenomenon as Symbiotic Modulation and hypothesize that it provides a mechanism to explain distribution patterns and phenotypic plasticity of plants growing across environmental gradients.
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1 - U.S. Geological Survey, 6505 NE 65th Street, Seattle, WA, 98125, United States
2 - University of Washington, Biology, Seattle, WA, 98195, United States
Presentation Type: Symposium or Colloquium Presentation
Date: Wednesday, July 30th, 2008
Time: 4:15 PM