Regulation Of Plant Nutrients To Heat Tolerance In Kentucky Bluegrass

Kentucky bluegrass (Poa pratensis) is a wideused cool-season turfgrass species due to its high turf quality and fascinating color even in winter. It is increasingly planted in transition zone recently. However, the climate with high temperature and high humidity in Yangtze River area causes a tough challenge for Kentucky bluegrass maintenance and turf quality. In this study, we conducted studies on the regulation of plant nutrients to heat tolerance in Kentucky bluegrass. The results were as follows:1. First study was to compare the responses of nutrients to heat stress between Kentucky bluegrass and bermudagrass. The heat injury in Kentucky bluegrass was significantly more severe than that in bermudagrass indicated by leaf photochemical efficiency and cell membrane peroxidation. High temperature caused the sharp decreases of N,P,K concentration in the leaves of Kentucky bluegrass, but no significant effect was observed in bermudagrass. Calcium and magnesium concentration increased in both species under heat stress and there was no significant difference between the two species. The results indicated that N,P,K nutrient levels may associated with heat tolerance of Kentucky bluegrass.2. The second study was to investigate the effects of foliar application of N,P,K on heat tolerance in Kentucky bluegrass. The results showed that high temperature treatment (35/30°C) caused the decreases of leaf photochemical efficiency, chlorophyll content, root activity, SOD,POD,CAT activity and N,P,K concentration whether nutrients applicated or not. Foliar application of KH2PO4, NH4NO3, and KH2PO4+ NH4NO3 inhibited the decrease of the above indexes in various ranges. The applications of NH4NO3 and KH2PO4+ NH4NO3 showed significantly increases of leaf photochemical efficiency, chlorophyll content, SOD,POD and CAT activity, the decreases of MDA content and electrolyte leakage. The effect of KH2PO4 was relatively lower than that of NH4NO3 and KH2PO4+ NH4NO3 treatments, only showed the significantly decrease of electrolyte leakage at 7d, 21d and MDA content at 21d.3. The third study was to investigate the effects of different nitrogen form on photosynthesis and heat tolerance of Kentucky bluegrass. The results showed that both different forms of nitrogen solution had positive effects on photosynthesis, nutrition situation and heat tolerance of Kentucky bluegrass. However, there was no significant difference between NH4+ and NO3- forms of nitrogen in turf quality, chlorophyll content, photochemical efficiency, net photosynthesis rate, Rubisco initial activity and activation.