Abstract:

Low temperature stress seriously affects the safe production of rice,especially machine-transplanted rice.In order to clarify the suitable plant growth regulator and spraying periods for machine-transplanted double-cropping rice,the early rice variety Zhongjiazao 17 and the late rice variety H you 518 were used as materials.The effects of different plant growth regulators(Uniconazole,C1;Abscisic acid,C2;Zhuanggubao,C3)and spraying periods(early rice:soak seeds,D1;one leaf and one core stage,D2;two leaves and one core stage,D3;before transplanting,D4;during the greening stage,D5;late rice:booting stage,F1;initial heading stage,F2;full heading stage,F3;one week after full heading,F4)on the yield and cold-resistant characteristics of machine-transplanted rice were studied.The results showed that among the three plant growth regulators,the Zhuanggubao treatment had the largest number of stems and tillers,the highest leaf area index,and the largest dry matter accumulation,which were significantly higher than the other two treatments.The yield of Zhuanggubao was the highest.The actual yield of early rice was 7.58% and 7.13% higher than that of uniconazole and abscisic acid treatments respectively.The actual yield of late rice was 13.54% and 11.59% higher than that of uniconazole and abscisic acid treatments respectively.In terms of spraying period,early rice was sprayed at the greening stage,and late rice was sprayed at the initial panicling stage,which had the best effect on improving various indicators of yield and the highest yield.Analyzing the components of yield,plant growth regulators and spraying periods mainly increased yield by increasing the number of grains per panicle of rice.The SOD,POD and CAT activities of early and late rice were highest in the grain-stuffing treatment.At the same time,spraying plant growth regulators during the greening stage of early rice and spraying plant growth regulators at the beginning of earing stage of late rice were more effective in increasing antioxidant enzyme activity.Taken together,the plant growth regulator for double-cropping machine-transplanted rice in Southern Hunan is Zhuanggubao,and spraying during the greening stage of early rice and spraying at the beginning of earing stage of late rice have the best cold-resistant and yield-increasing effects.

Key words: Double-cropping rice, Machine transplanting, Plant growth regulator, Yield formation