| Creeping bentgrass (Agrostis stolonifera L.) is one of the cold-season turf grasses which are used to build high-quality turf. However, it is hard to survive the summer in the middle and lower Yangtze area, its optimum growth temperature ranges from 15 to 24℃. Therefore, improving heat resistance of creeping bentgrass and extending green period are important in turf management in the middle and lower Yangtze River. Salicylic acid(SA), which is a kind of small molecular phenolic and widely exists in plant, is an important signal molecule for disease resistance response of plants. Furthermore, exogenous SA could improve the heat resistance of plant. Thus, the objectives of this study were to research the differences of heat resistance among varieties of creeping bentgrass and to explore the appropriate SA concentration for creeping bentgrass in turf management practice in summer and the duration of improving the heat resistance by SA in order to provide theoretical reference for the scientific use of SA.Heat resistance of seven varieties was evaluated in simulated high temperature stress. The results showed that the heat resistance differed significantly among the varieties, and the heat resistance was Alpha > Penncross > putter > Bengal > PennA-1> pennA-4> Regent. Alpha had a high ability of heat resistance, because of high antioxidation capacity of membrane, which kept slowly leave growth under the heat stress condition.SA with different concentration of 0, 5, 10, 20, 40μmol·L-1 were respectively irrigated to creeping bentgrass after 6 days culturing under continuous high-temperature stress with 38℃/30℃(day/night). The results showed that the average leaf growth rate of the 10μmol·L-1 SA treated plant was significantly higher than that of the control (p <0.05); leaf ROS and leaf MDA content of 5～20μmol·L-1 SA treated plants were remarkably lower than that of the control (p <0.05). The SOD activity evidently increased by SA irrigation, which may play a crucial role in reducing heat hurt on creeping bentgrass. In this study, the effect of the treatment of 10μmol·L-1 SA on heat resistance was the best and could be used as a referential concentration in practice.Tenμmol·L-1 SA was irrigated to creeping bentgrass under heat stress and the results showed that on the 4 th day after heat stress, the average growth rate of SA treated plant was significantly faster than that of the control (p<0.05); the content of MDA and ROS in leaves reached the minimum in the 3rd and 4th day then increased. SOD activity increased continuously during the 6 days. There was no significant difference in SOD activity and content of ROS and MDA of leaves between the treated and control(p p<0.05 )on the 6th day. The average growth rate of the treated plant reduced to 0mm .d-1. The results suggested that the heat resistance of grass treated with SA lasted about 6 days under heat stress. The treated grass was irrigated again with the same concentration on the 5th day, the results showed that the heat resistance of creeping bentgrass could be induced once again and the heat tolerance ability can last for 12 days.The above results indicated that the turf with excellent heat tolerance such as Alfa et al, treated with SA can over summer well in hot summer areas. The turf quality of creeping bentgrass treated with SA can also be improved.
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