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Predicting mycorrhizal effects on stomatal conductance.
AUGÉ, ROBERT*,1, MOORE, JENNIFER1, CHO, KEUN HO1, 1 University of Tennessee, Knoxville, TN
ABSTRACT- Arbuscular mycorrhizal symbiosis often affects stomatal conductance (gs) of leaves of host plants. However, experimental results have been sporadic and scientists have been unable to predict with any confidence when mycorrhizal promotion of gs is likely to occur. We tested whether mycorrhizal influence on gs was more pronounced under some environmental conditions than others. In greenhouse-grown Sorghum bicolor, mycorrhizal promotion of gs, relative to nonmycorrhizal plants of similar size, was much less at either end of naturally occurring ranges of irradiance, air temperature and leaf temperature. A similar trend occurred when mycorrhizal promotion of gs was examined as a function of leaf−air temperature difference. Mycorrhizal promotion of host gs was remarkably similar whether plant roots were colonized by Glomus intraradices or Gigaspora margarita. Diminished mycorrhizal effects at the lower and upper limits of irradiance and temperature ranges were not related to absolute gs. Effects of Glomus intraradices tended to be greater in the afternoon than in the morning.
KEY WORDS: stomatal conductance, arbuscular mycorrhizal symbiosis, irradiance, temperature