Abstract:

【Objective】 The effects of spraying exogenous hormones(gibberellin-3, GA3; brassinolide, BR and 6-benzylaminopurine, 6-BA) at early (July 6) and full (July 17) flowering time on physiological characteristics of main stem functional leaves at flower and boll stage. 【Method】 Three exogenous hormone treatments were emploid, with two concentration levels each, i.e. GA3 10 and 30 mg•L-1, BR 0.01 and 0.1 mg•L-1, and 6-BA 10 and 100 mg•L-1,with spraying water as the control(CK). The contents of chlorophyll, soluble protein, malondialdehyde, soluble sugar, endogenous hormone contents and the activities of superoxide dismutase (SOD) and peroxidase (POD) were measured. 【Result】 The results showed that the treatment of 100 mg•L-1 6-BA significantly increased the contents of chlorophyll, soluble protein, soluble sugar and the activities of SOD and POD at full flowering stage. The treatments of 6-BA 100 mg•L-1 and GA3 30 mg•L-1 significantly increased the contents of GA3 and ZR, and the ratio of ZR (zeatin riboside) / ABA (abscisic acid ),GA3 /ABA, and (ZR+GA3)/ABA at the same stage. The content of MDA greatly decreased. The treatments of BR (0.01 mg•L-1) and GA3 (10 mg•L-1) also had a positive effect, but the effect was weaker. The treatments of GA3 30 mg•L-1 and 6-BA 100 mg•L-1 significantly increased the content of soluble protein, the ratio of GA3/ABA, GA3+ZR/ABA, while the content of MDA significantly decreased at full bolling stage.【Conclusion】 Under this experimental condition, spraying 6-BA 100 mg•L-1 and GA3 30 mg•L-1 had significantly effects on the physiological functions of main stem functional leaves, it could be used for delaying the senescence of cotton.

Key words: cotton, flower and boll stage, stem leaves, exogenous hormones, physiology characteristics