Abstract: 【Objective】 The purpose of this study was to illuminate the sensibility of the exogenous hormones to the plant height characters of a new dwarf mutant AS98 and determine which kind of hormone deficiency this mutant belongs to. 【Method】Two cotton lines, dwarf mutant AS98 and normal type LHF10W99, were used as materials in this research. AS98 was treated with different contents of exogenous GA3, IAA and BR. The changes of plant height, internode length and leaf number were investigated in different treatments. Meanwhile, the activities of α-amylase, POD and SOD of the mutant were analyzed after the mutant AS98 was treated with GA3 and PP333. 【Result】 The result indicated that the average plant height, internode length, boll weight and seed index of AS98 without hormone treatment were markedly lower than that of normal genotype LHF10W99, respectively, but their leaf number and lint percentage were not significantly different compared with that of LHF10W99. After being treated with 100 mg•L-1 exogenous GA3 continuously, the plant height and internode length of AS98 showed very significant difference compared with AS98 without being treated with hormone, and reached that of the normal type of LHF10W99. But the plant height and internode length of AS98 treated with IAA and BR did not show significant difference with that of the control. The regression analysis showed that there was a significant relationship between the exogenous GA3 and plant height, internode length of mutant AS98, but there was no significant relationship between the plant height and IAA and BR. Moreover, the exogenous GA3 could increase the α-amylase activity of AS98 and decrease POD and SOD activities. On the contrary, PP333 could reduce the α-amylase activity of AS98 and up-regulate POD and SOD activities. 【Conclusion】 It is concluded that AS98 is a new super-dwarf mutant with normal broadleaf. The plant height of AS98 is sensitive to the exogenous GA3, and can be resumed to normal height with exogenous GA3 continuous treatment. The α-amylase activity of AS98 is sensitive to exogenous GA3 and PP333. AS98 is a GA3-deficiency dwarf mutant.

Key words: cotton, mutant, GA3-deficiency, hormone, enzyme activity