Metabolic Responses to Heat Stress for Two Agrostis Grass Species Contrasting in Heat Tolerance.

Heat stress is one of the most important factors limiting growth of cool-season grasses in the transitional and warm climatic regions. The responses of some turfgrass species to high temperature have been investigated at the gene and protein levels. However, functions of the complex stress signaling pathways are yet to be determined at the metabolic level. The objectives of this project are to analyze changes in major metabolites under heat stress in two Agrostis species that differ in heat tolerance, and to determine major metabolic metabolisms regulating bentgrass heat tolerance. Plants of heat tolerant A. scabra Willd. and heat sensitive A. stolonifera L. ‘Penncross’ were exposed to the optimum temperature of 20°C and superaoptimal temperature of 35°C for 10 days in growth chambers. The variation in heat tolerance between the two species was reflected by differences in photochemical efficiency and chlorophyll content measurements, with greater declines in A. stolonifera after heat treatment. The type and content of polar metabolites in shoot and root samples were analyzed using GC/MS. Differential metabolic responses between A. scabra and A. stolonifera were exhibited in the accumulation of amino acids, organic acids, and carbohydrate metabolism. Heat injury in bentgrass was associated with the inhibition of amino acids and organic acids biosynthesis.