Physiological responses of C4 grasses to prolonged heat stress

C4 grasses are best adapted to the transition, warm-arid, and warm-humid climatic zones and have the ability to acquire thermotolerance by exposure to acute heat stress. Exposure to sub-lethal temperatures results in changes in physiological, biochemical, metabolic, and molecular processes. The response of two warm-season grasses to prolonged heat stress was investigated. Plants of hybrid bermudagrass (Cynodon dactylon × C. transvaalensis ‘Tifway’) and Japanese lawn grass (Zoysia japonica Steud. ‘Meyer’) were exposed for 168 h to supraoptimal temperature conditions (47°C) in controlled-environment chamber. Compared with zoysiagrass, bermudagrass showed greater damage. Metabolite profi les were affected by prolonged heat exposure, with signifi cant differences between these species. Consistent differences were found in total soluble sugars accumulation over the study period and severity of plant organ senescence. Bermudagrass roots were more affected, as compared to leaves. Leaf proteins expression determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis showed an early degradation in zoysiagrass, as thermal exposure proceeded. A signifi - cant net decline in protein content was observed after 48 h of exposure, while in bermudagrass an analogous decline was not detected until 96 h of treatment. Although heat stress is not considered a detrimental factor to C4 grass species, the two species showed signifi cant differences in their physiological response to continuous high temperatures.