Growth, Nutrition and Gas Exchange of Bromus Inermis Inoculated With Glomus Fascicula Tum

SUMMARY Plants of Bromus inermis Leyss. inoculated or not with the mycorrhizal fungus Glomus fasciculatum (Thaxter sensu. Gerd.) Gerd. and Trappe, were pre‐conditioned at two soil moisture levels (Φ s − 0.03 or − 0.8 MPa) for 17 weeks, then subjected to a drying cycle. Stomatal conductance (g 1 ), soil‐plant liquid flow resistance ( R s−p ), and photosynthesis rates ( P s ) were measured before, during, and after the drying cycle. Soil water stress and mycorrhizal inoculation significantly reduced plant top dry weight during the 18 week study. Chlamydospore production by the mycorrhizal symbiont G. fasciculatum was significantly increased by soil water stress of −0.8 MPa. Foliar Ca and Mg concentrations were significantly greater in mycorrhizal plants. Foliar concentrations of P, K, N, Mn, Zn and Cu were significantly greater in drought stressed plants whereas Ca and Mg concentrations were significantly greater in well‐watered plants. Mycorrhizal plants pre‐conditioned at Φ s −0.8 MPa had 36 and 34% lower R s−p values than nonmycorrhizal plants at pre and peak drought sampling times, respectively. Following re‐irrigation, g 1 was 64% greater in mycorrhizal plants when compared to nonmycorrhizal plants. Inoculation with G. fasciculatum increased photosynthesis rates by 20, 52, and 22 % over the noninoculated plants before, during, and after the drying cycle respectively. Despite increased rates of photosynthesis, top dry weight of mycorrhizal plants was 15 % less than that of noninoculated plants. Regardless of inoculation treatment, plants pre‐conditioned at Φ S −0.8 MPa exhibited greater g 1 and P s values during and after the drying cycle. Bromus inermis demonstrated the ability to adapt to water deficits. Mycorrhizal symbiosis may play a role in the adaptation of B. inermis to dry sites.