Impact of a Horizontally Transmitted Endophyte,Balansia henningsiana, on Growth and Drought Tolerance ofPanicum rigidulum

Abstract

The impact of the horizontally transmitted endophyte Balansia henningsiana on the growth of C4 grass Panicum rigidulum was examined in the greenhouse under control and drought‐stress conditions. Tiller number, leaf number, and the root:shoot ratio were higher and shoot height and leaf area were lower for infected (E+) than for uninfected (E−) plants. Under control conditions, the total biomass was similar for E+ and E− plants. Under drought‐stress conditions, however, E+ plants had less biomass. In response to drought stress, E+ plants reduced leaf growth and increased leaf senescence more than E− plants. After recovery, E+ plants responded by more rapid leaf growth and allocated more resources to the leaf than to the root. Under control conditions, the photosynthetic pigment content of E+ leaves tended to be higher than that of E− leaves. With decreasing leaf water content, the difference in pigment content between E+ and E− plants became smaller. Endophyte infection had no effect on net CO2 assimilation rate or transpiration rate and thus on water use efficiency, regardless of water status. Overall, B. henningsiana was not beneficial to host growth during drought stress. However, infection facilitated rapid leaf regrowth of the host grass after soil water became available.