| With the material of Lumianyan28, transgenic insect-resistant cotton generalized in large aera, two water treatments were set with drought (RWC<60%) and CK (RWC as normal) to determinate such indexes of cotton leaves as photosynthesis, fluorescence, contents of chlorophyll, soluble sugar, soluble protein and endogenous hormones. Also, antioxidant enzymes and their isozymes expression have been researched. Besides, we tested boll quality, lint percentage and single boll weight at different sites of cotton, plant height and leaf area at different times. The results as follows:1. Leaf water potential in drought condition was decreaser than that of CK at most times accordingly. The chlorophyll content was higher significantly than that of CK, but the Chl.a/b was lower significantly than that of CK at the same time, which stating soil drought resulting to leaf water deficit, the extent of thylakoid stacking decreased and thereupoun photosynthesis weaken.2. Under drought treatment, the photosynthesis rate and stomatal conductance were increased evidently in seedlingstage. Transpiration rate was increased evidently in bud stage with drought, which illustrated it causing plant water lost in some extent, was a chief driver of passive absorption of water in a larger sense, indirectly reflecting the resistance of crop to drought stress. The changing trends of intercellular CO2 concentration (Ci) with two treatments were similar: Ci of cotton main stem leaves under drought treatment was higher significantly than that of CK in bud stage and in flowering and boll-setting period.3. Initial fluorescence (Fo) low at first was very significantly higher under drought treatment than that of CK at initial flowering stage. Photo-chemical efficiency of PS II (Fv/Fm) with drought were lower significantly than that of CK at initial flowering stage and boll stage when the cotton were suffered drought stress seriously. Photosystem II (PS II) under drought stress had been very significantly lower than that of CK after initial flowering stage, showing that drought mainly influenced photosynthetic electron transport at middle and later stage of cotton development. The changing trend of electron transport rate (ETR) was similar to that of net photosynthesis rate, and both were also significantly correlated. Photochemical quenching (qp) was very significantly higher under drought treatment than that of CK at bud stage, which was possible because soil drought accelerated reproductive growth of plant. Non-photochemical quenching coefficient (NPQ) with drought was lower significantly than that of CK at initial flowering stage when the plant was sensitive to soil drought and the ability of photo-protection was weak.4 The soluble protein content in main stem leaves and in middle-fruit branch leaves under drought treatment, showing decreasing dynamic changes generally then increasing at end time, were higher than that of CK, the normal soil water management treatment. Lower-fruit branch leaves under drought treatment had lower protein content during boll age 20 day than CK treatments.5 From June 25 to July 22, the activity of superoxide dismutase (SOD) in main stem leaves under drought treatment was lower than that of CK. Other time periods had varying results. The peroxidase (POD) activity in main stem leaves and in fruit branch leaves was lower at early stage, and then higher at late stage. The catalase (CAT) activity showed an increase-decrease trend, higher in main stem leaves under drought treatment than that of CK. However, it was opposite in the lower fruit branch leaves, and there were no significant differences between the two CAT treatments in the middle branch leaves. Under CK treatment, the soluble protein content and the CAT activity of the lower fruit branches leaves had a highly significant correlation (n=7, r=0.934**). It is suggested that the soluble protein and catalase activity of lower branch leaves were related closely. The middle branch leaves play important physiological functions in the early growth stage under drought stress.6. ZR contents in main stem leaves both showed single peak curves under two treatments, and which was very significantly higher but later under drought condition than that of CK. The GA3 content of drought leaves showed second-order peak value, making plants enter reproductive stage earlier. IAA content was increased at metaphase in drought stress, but there was not obvious difference in variation tendency between two treatments. It took on a higher peak value of ABA in early drought leaves, and later, ABA ascending slowly to promote premature. Also, drought influenced the dynamic balance of ZR/ABA,GA3/ABA,IAA/ABA and (ZA+GA3)/ABA. It took longer actions of ZR under drought condition; GA3/ ABA were related closely in the hormone mutual actions; IAA/ABA played an important physiology role at later growth even in water deficiency.7 The degree of membrane lipid peroxidation increased significantly at initial flowering stage and at full-bloom stage. There were no obviously increasing trend for malondialdehyde (MDA) contents of middle and lower branch leaves along with boll ages prolongation.8 The soluble sugar content of main stem leaves under drought was all higher significantly than that of CK during cotton growth stage (September5 exception), indicating that the output of organic was influenced greatly by soil drought stress. The same effect existed in middle branch leaves under drought on boll age20, which was possible for the middle branch leaves were key elements to the boll development.9. SOD isozyme expressed 3 bands at seedling and bud stage under drought stress. Later, the forth band appeared; Bandâ… expressed stronger and stronger, may being related to enhancement of SOD activity in late stage, and showing that SOD isozyme take certain actions after middle stage under drought stress.With two treatments, POD isozyme appeared two obvious bands that become stronger and stronger as the growth promoting, the changing trend was consistent to that of the POD activity. However, the mobilities of POD isozyme with two treatments were different possibly for the configurational change of POD enzyme molecular under water stress.The expression of CAT isozyme under drought treatment showed stronger early, then weaker later, showing it was consistent to the characteristics of POD activity in some extent. For the CK treatment, also, there were two bands early, but weaker than that of drought, which illustrated drought had influenced the expression of CAT genes.10. The plant height, along with leaf area and single boll weight, was highly lower significantly under drought treatment than that of CK. Also, the fiber length, specific breaking strength, elongation of upper cotton fiber and mic value of middle and lower cotton fiber were decreased significantly suffered drought stress. However, there was obvious influence for uniformity of cotton fiber under drought stress.
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