Endophyte infection accelerates morpho‐physiological responses to water deficit in tall fescue

Abstract

Abstract Endophyte‐infected (E+) tall fescue plants are usually more persistent under water deficit than endophyte‐free plants (E‐). The reason for this is still unclear because of conflicting reports about growth and water status variables. A glasshouse experiment was carried out to compare morpho‐physiological responses of E+ and E‐ tall fescue plants to water deficit during a cycle of water deprivation and recovery. Under non‐limiting conditions total dry mass per container was higher in E+ plants than in E‐ plants. However, no differences were found between endophyte treatments in root:shoot ratio, water status or in reducing sugar content of leaf blades or tiller bases. Under water limiting conditions an accelerated response to water deficit was observed in E+ plants. The relatively steeper growth cessation as well as higher leaf and root senescence in E+ than in E‐ were linked with a higher accumulation of sugars within the stem base of E+ plants which also tended to show a more pronounced decrease in water potential. Under water limiting conditions relative root: shoot ratio tended to decrease in E+ while remaining unchanged in E—. Following re‐irrigation, a general recovery in growth and water status variables was observed. A simple explanation is proposed to reconcile our results with previous reports, although further research is needed.