关键词: 化学打顶, 棉花, 外源物质, 脱叶率, 吐絮率, 产量

Abstract: To investigate the effects of different exogenous substances on defoliation ripening, yield and quality of cotton after chemical topping, Xinluzao 67 was planted according to field experiment in Dafeng town (Hutubi county, Xinjiang) . After chemical topping, three doses of exogenous substances were sprayed on the leaf, including dimetyl piperidinum chloride (DPC, 75, 150, 225 g·hm^-2), uniconazole S-3307 (S-3307, 150, 300, 450 g·hm^-2), brassicin (BR, 0.375, 0.75, 1.125 g·hm^-2) and gibberellic acid (GA, 150, 300, 450 g·hm^-2), while water treatment was for control. The seed cotton yield was investigated and the cotton fiber quality was analyzed. The results showed that spraying of different exogenous substances afer chemical topping had an enhanced effect on cotton leaf-stripping and wadding, and the leaf-stripping and wadding rates were increased by 5.05%~17.59% and 11.61%~32.87%, respectively, compared with  CK, which had an influence on the hanging twig rate but not significant. The medium dose (0.75 g·hm^-2) of BR had the best defoliation effect, and the defoliation rate reached 95.33%. The ripening effect was the best in low dose of BR (0.375 g·hm^-2), and the wadding rate reached 98.11%. All treatments had  significant effects on cotton yields and qualities. BR treatment with medium dose (0.75 g·hm^-2) had the highest seed cotton yield, which was significantly increased by 19.27% compared with CK. GA treatment with medium dose (300 g·hm^-2) had the best performance in fiber quality. Medium and low doses of BR (0.375~0.75 g·hm^-2) and medium and low doses of GA (150~300 g·hm^-2) could enhance the effects of defoliation and ripening after chemical-toped cotton, effectively increase the seed cotton yield and optimize the fiber quality of cotton.

Key words: chemical topping, cotton, exogenous substance, defoliation rate, boll opening rate, production