Alleviation Effects Of Elevated CO₂ On Physiological And Biochemical Responses To Temperature And Water In Tall Fescue

Tall fescue (Festuca arundinacea) is a cool-season trufgrass and forage grass which widely distributes all over the world. Tall fescue adapts transitional zones between cool-wet and warm-wet areas and is extensively used in schools, parks, sports ground and golf courses, et ac. Tall fescue is a bunch type grass established from seeds, with strong tiller, developed fibrils, powerful resistant to heat, disease, cold, drought, acid, barren and trample. It could make early, dense and fast growing lawns with lower maintenance so that it is one of the more welcome turfgrass. Taking tall fescue as target material, we (1) studied how elevated CO2 alleviated the effects of transitional drought on physiological indexes; (2) elaborated the alleviation of CO2 enrichment on physiological indexes in response to elevated temperature (5℃above normal temperature); (3) discussed the interactive effects of elevated CO2, elevated temperature and drought on physiological indexes; (4) studied the responses of physiological and biochemical indexes to elevated CO2 under heat stressed conditions to look for mechanisms from protein and metabolism levels; (5) studied the effects of non-transitional drought and rewartering treatment on all indexes under elevated CO2 conditions.Taking tall fescue as material, the physiological and biochemical responses to elevated temperature and transitional drought in conditions of CO2 enrichment were studied under climate change scenario in chapter 3. Results showed that elevated CO2 mitigated the adverse effects of elevated temperature and drought in tall fescue, including decreased stomatal conductance, SWC, and RWC, but increase photochemical efficiency and electrolyte leakage to reduce water loss and protect cellular integrity to improve photosynthesis and decrease respiration. Additionally, elevated CO2 could significantly decrease stomatal limitation to photosynthesis and this effect was not affected by temperature elevation and transitional drought.Successive high temperature in summer is one of the pretty important abiotic factors affecting cool-season turfgrass growth. Chapter 4 would elaborate how cool-season turfgrass responds to long term heat-stressed environment under elevated CO2. Results indicated that heat stress seriously affected the normal growth and metabolism, including decreases in A, Ci, gs, WUE. TQ, Gr, SLA, Jmax, cellular stability, Rubisco activity and activation state, while elevated CO2 suppressed their decreases. Results showed the protective effects of elevated CO2 on tall fescue under heat stress.High temperature always accompanying with little precipitation in summer impose negative effects on turfgrass. Chapter 5 elaborated how tall fescue response to drought stress and rewartering under elevated CO2 concentration.100% drought stress induced the rapid decreases in SWC, RWC, A, gs, Tr, Rubisco activity and activity state. SWC, RWC, A, gs and Tr recovered to 0 d (without treatments) after rewartering for one week, but Rubisco activity and activity state still had significantly lower values than those of 10 d of drought treatment indicating that server drought caused irreversible injury to Rubisco activity and Rubisco activase.In conclusion, elevated CO2 could significantly mitigate the adverse effects of temperature and drought stresses on physiological and biochemical indexes in tall fescue. The alleviation effects of elevated CO2 could improve heat and drought tolerance which is better for responding to global climate change.