Effects And The Regulation Mechanism Of Exterior Antioxidants On Thermotolerance In Tall Fescue

Tall fescue has been widely used for establishment of sports fields, courtyard and beautification because of their long-green periods, better heat tolerance and disease resistance. The optimum temperature for tall fescue ranges form 15 to 24℃for shoot growth and 10 to 18℃for root growth, so it can hardly survive heat and drought stress in the transitional zones in summer. The trial studied the effects of exterior antioxiants on seed germination and thermotolerance of tall fescue for the mechanism and appropriate concentration. The main results were as follows:1. The stability of content of chlorophyⅡand relatilve water, activity of antioxidant enzymes and other physiological indexes of tall fescue displayed much better under 25/20℃(day/night) than under 35/30℃(day/night). The contents of AsA and GSH increased and AsA-GSH recycle was improved by being treated with V_c. Mannitol could not significantly improved antioxidants content compared with V_c, but it could keep the stability of antioxidant enzymes much higher. So the plant grew well with mannitol.2. The activities of SOD, POD, APX in CK enhanced and N and K uptake increased during early heat stress under 35/30℃as dry matter increased, and these physiological indexes decreased at late heatstress. It means high temperature is the main reason for leaf chlorosis and plants senescence. The results also indicated the activities of antioxidant enzymes in root were much lower than those in shoot, but the decreasing rates of these indexes were larger than those in shoot. It suggested that heat sensitivity of root was larger than that of shoot3. V_c improved the content of antioxidants and activities of antioxidant enzymes, synergetic effect of which could clear away reactive oxygen species and reduce lipid peroxidation and decelerate the chlorophyⅡdegradation under heat stress. The plants treated by mannitol, whose variation of antioxidant enzymes and MDA were smaller and pigments content were higher than those of CK and V_c.V_c and mannitol were two effective scavengers of active oxygen species, and lmmol/1 mannitol was more efficient.4. The activites of SOD, POD, CAT, APX enhanced and content of soluble protein and relative water increased when tall fescue were treated with mannitol. Mannitol could enhance the integrity and stability of membrane. The study showed when manntiol was lmmol/1, the protection effect from heatstress was best. Mannitol could also promot the seeding growth of tall fescue when its concentration were 0.1 and lmmol/1. The length of shoot and root, content of chlorophyⅡand carotenoid and flesh weight of tall fescue increased significaly (P＜0.5) by treated with Manntiol in these two levels and 0.1mmol/1 much better. When the concentration was 10 mmol/1, it declined the germination percentage of seeds and was unfavorable for growth.