Abstract: Super hybrid late rice variety WufengyouT025 was used as test material as well as the treatments of spraying foliar fertilizers for 3 concentrations of potassium dihydrogen phosphate (KH2PO4) with 0.1% (P1), 0.3% （P3), 0.5% (P5) and the control for clear water (CK) were set. The effects of spraying P and K fertilizers on the leaf temperature, yield and physiological characteristics in double-season late rice under low temperature conditions during heading and flowering stage were studied. The results showed that rice leaf temperature under the different foliar fertilizer application treatments was higher than that of CK, and the warming effect of treatment P3 was the best during the low temperature period. Leaf chlorophyll content and net photosynthetic rate (Pn) of rice plants decreased gradually with the treatments under low temperature, while the reduction range was the smallest in treatment P3, variation of the different treatments on transpiration rate (Tr), stomatal conductance (Cs), and intercellular CO2 concentration (Ci) presented the same character. The activities of the antioxidative enzymes varied in different degrees and the activities of superoxide dismutase (SOD) and peroxidase (POD) in CK was the highest and P3 was the lowest, while the activity of catalase (CAT) was opposite in the mass that CK was the lowest and P3 was the highest after low temperature advance. Malondialdehyde (MDA) content for the different treatments increased in different degrees after low temperature advance, and that in P3 was the lowest. Under low temperature, foliar spraying potassium dihydrogen phosphate and potash could improve dry matter accumulation to varying degrees during yellow ripening stage, especially panicle dry matter accumulation and achieve the purpose of slowing down the yield decrease, among which treatment P3 was the best. Yield of P3 at the second sowing date (sowing in July 1st) in 2015 encountering low temperature obviously increased by 14.04% compared to CK. It could be found from the yield components that effective panicles per plant, the total grains per panicle, seed setting rate were significantly improved for the all treatments compared to CK. The application of foliar spraying of 0.3% potassium dihydrogen phosphate was the most effective agronomic measure to enhance the resistance to low temperature during heading and flowering stage for double-season super hybrid late rice.

Key words: Double-season late rice, Heading and flowering stage, Low temperature resistance, Spraying foliar fertilizer, Cold dew wind