| Contrasting with the warm-season turfgrasses, the cool-season turfgrasses are more and more welcomed for their long-green periods, soft-qualities, brilliant-colors, and their good-lookings. The special climate characters ie high temperature and drought stress handicap the growth of the cool-season turfgrasses which would be inclined for cool and warm climate. Physiological and biochemical mechanisms of 6 different cool-season turfgrass cultivars( Baron, Node, Sabre, Barlexas, Houndog and Alligator ) under heat stress and drought stress were systemicaliy studied, green leaves were numbered, chlorophyll contents (including Chla and Chlb ),and electrolyte leakage(EL) ,contents of the lipid peroxidation product-malondialdehye (MDA), contents of proline(Pro),and activities of 3 major antioxidant enzymes ie superoxide dismutase(SOD), catalase(CAT), and peroxidase(POD) in fresh leaves were determined every other day during 20%-PEG drought stress or 42 heat stress, and the relationships between the antioxidation abilities and heat or drought-resistance were preliminarily studied. The main results and conclusions were as follows.(1) Among the 6 cool-season turfgrass cultivars, different cultivars held different drought-resistance and their own physiological and biochemical mechanisms during the drought stress. Poa pratemis L. cv(Node) was the most resistant to drought stress, while Poa trivialis L. was weakest, and Festuca arundinacea Schreb was more resistant than Lolium prenne L. . Poa pralemis L. and Poa trivialis L. both belonging to the same genera had obviouse drought-resistances, the physiological and biochemical mechanisms of them were also different: more green leaves, more content of Pro, more activities of SOD, POD, CAT, and less content of MDA, or less leakage of electrolytes from cells occurred in Poa pratensi.s L. which had more resistance than Poa trivialis L. .(2) Green leaves, chlorophyll content decreased constantly, whereas EL, content of MDA and Pro increased constantly under drought stress in the 6 different cool-season turfgrass cultivars; The activities of SOD, POD and CAT firstly increased slowly thendecreased under the drought stress in the 6 cool-season turfgrass cultivate: in most of the 6 cool-season turfgrass cultivars, the activities of SOD, POD reached maximum values in 6d, while others' activities of SOD reached the highest level in 4d or 8d; the activities of CAT reached the highest content in 2d then decreased constantly with the drought stress progressing, and down lower than the levels in 0d.(3) Green leaves, chlorophyll content decreased constantly, whereas EL, content of MDA increased constantly under heat stress in the 6 different cool-season turfgrass cultivars; and the content of Pro and the activities of POD firstly increased slowly then decreased under the heat stress, and reached their maximum values in 2d and 4-6d during heat stress respectively; the other two antioxidant enzymes ie SOD, CAT changed in difference respectively the activities of SOD increased constantly in all of the 6 cool-season turfgrass cultivars while in one of the 6 cultivars the activity of CAT decreased constantly but in other 5 of the 6 cool-season turfgrass cultivars the activity of CAT firstly decreased then increased and declined again at last, in both cultivars of Poa pratensis ,L, grew up above the control condition.(4) Among the 6 cool-season turfgrass cultivars, different cultivars held different heat-resistance and their own physiological and biochemical mechanisms during the heat stress. Poa pratensis L. cv(Node) was the.most resistant to drought stress, while Lolium prenne L. was weakest. Although the content of MDA was more in Poa pratensis L. cv(Node) than in Lolium prenne L. , it held the most or secondly most activities of the 3 antioxidant enzymes in all of the 6 cultivars and had.the secondly most content of Pro while Lolium prenne L. held the lest content of Pro and the:.lest activities of the 3 antioxidant enzymes. As for the Poa pratensis L, cv(Baron) and the F...
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