The Metabolic Effects Of Elevated Carbon Dioxide On Bermudargass Tolerance To Heat Stress

Elevated temperature and CO2 concentration are the two major characteristics of global climate changes.High temperature is the key limiting factor for grass management during summer,which could cause severe damage on the plant growth and development.It has been reported that elevated CO2 concentration can improve the plant tolerance to the abiotic stress,however,the mechanism underlying the positive effects of elevated CO2 on bermudagrass(Cynodon dactylon)tolerance to heat stress is unclear.The objective of this study was to identify the physiological,metabolic and protemic responses to elevated CO2 on hybrid bermudagrass(C.transvaalensis X C.dactylon cv.'Tifway'),a C4 perennial grass species subjected to heat stress.Plants were planted under either ambient CO2(400 ?mol·mol-1)or elevated CO2(800 ?mol·mol-1)and subjected to control temperature(30/25?,day/night)or heat stress(45/40?,day/night).The main results are as follows:1.Compared with that in the ambient CO2 concentration,the electrolyte leakage(EL)of bermudgrass leaf,exposed to heat stress for 28 days,was significantly decreased by elevated CO2,while the chlorophyll content(Chl),net photosynthetic rate(Pn),and Chlorophyll fluorescence parameter(Fv/Fm)increased to some extent.It suggested that elevated CO2 can reduce heat-induced damages through enhancing the stability of membrace and photosynthesis ability.2.Based on the GS-MS technology,we analyzed the metabolite changes of bermudagrass leaf under different CO2 concentrations.It was found that the content of organic acids,amino acids,sugars and sugar alcohols increased in leaves exposed to elevated CO2 compared with ambient CO2 under heat stress,suggesting that CO2 could improve the heat tolerance in bermudagrass through promoting the glycolysis and TCA cycle of respiration,as well as the amino acid metabolism and GABA shut.3.Using the two-dimensional electrophoresis technology,we analyzed the differentially expressed proteins responsive to elevated CO2 concentration under both temperatures.It was found that the proteins involved in light reaction and carbon fixation of photosynthesis were up-regulated by the elevated CO2,which also stimulated the proteins accumulation in glycolysis and TCA cycle of respiration.Those up-regulated metabolic pathways could contribute to the improvement of heat stress.