Nitrogen Rate On Growth And Physiological Response Of Tall Fescue Turf Grass Under High Temperature

High temperature is the major factor limiting growth of cool-season turf grass in transitional zones. The optimum temperature for cool-season turf grass range from 15 to 24 C for shoot growth and 10 to 18 C for root growth. It can be evergreen year round in cool climate zone. In Yangtze River transitional zones it has long green period. But in summer, it can hardly survive from heat stress. The trial studies the effects of nitrogen on tall fescue, a cool-season turf grass, under heat stress by four nutrient solutions concentration such as NO (0mmolN/L), N3 (3mmolN/L), N6 (6mmolN/L) and N9 (9mmolN/L) .The main results were as follows:1. The biomass , chlorophyll and other physiological index of tall fescue under optimum temperature were increase as nitrogen level increase, which manifest nitrogen effective.2. The biomass of tall fescue turf grass with N6(6mmol N /L) , N9(9mmol N /L) treatment reached its climax in 30/25 C, and then decreased rapidly. So did the chlorophyll and carotenoid content, POD and SOD activity , root activity. But index of N0(0mmol N/ L), N3(3mmol N/ L) treatment reached its climax in 35/30 C, and then decreased. It suggested that stress temperature of high nitrogen level is lower than that of low nitrogen level.3. When the temperature was higher than 35/30 C, proline and MDA content of shoot were more than those of root. But the increasing rate of proline and MDA content in root were more hgher than those of shoot, and the decreasing rate of root biomass , root activity, SOD and POD activity were larger than those of shoot. It suggested that heat sensitivity of root was larger than that of shoot.4. Under the utmost heat stress(40/35 C), tall fescue plants of N9 treatment died 3 days after treatment(DAT), and N6 treatment died 6 DAT, NO and N3 treatment still lived 9 DAT. But the biomass and chlorophyll content of N3 treatment were more than NO treatment, while other index were less than NO treatment. The result shows that suitable nitrogen level could improve the overall quality of tall fescue turf despite decreased its heat tolerance to some extent.5. Employing nitrogen fertilizer suitably in summer was one of the management to improve tall fescue turf quality. In this study, the effect of N3 treatment was the best, and N6 treatment followed, NO and N9 treatment was the worst.