棉 花 学 报 Cotton Science 2007，19(6)：467-471
Regulation Effects of Exogenous 6-BA on Photosynthesis and Leaf Senescence in Cotton Abstract：Compared to control (CK)，the plant height，leaf number，leaf area，and dry weight per plant were all increased in the treatment with exogenous 6-BA in the tested cotton cultivars. The chlorophyll content，soluble protein content and photosynthetic rate in the lower-position leaves of plant were higher in the 6-BA treatment than those in CK，but the 6-BA effects varied on above parameters among the cultivars. The highest effects was found in 33B，the senescent-sensitive cultivar，then in 20B，the mid-senescent type cultivar，and the lowest in Fengkang 6，the senescent-resisting cultivar. 6-BA application increased the superoxide dismutase (SOD) activities and peroxidase (POD) activities，and decreased the MDA contents in the tested cultivars，showing that the exogenous 6-BA has a role for plant to enhance the capabilities of active oxygen scavenging and lessen the over-oxidation degree of cytoplasm membrane. Therefore，the improvement of balance level between the process of producing active oxygen species and corresponding scavenging capability during the mid- and late-leaf growth stages，was possibly the important physiological mechanism that the leaf photosynthetic rates were increased and leaf senescences were delayed in the treatment with exogenous 6-BA Thus，in cotton production，exogenous 6-BA has possibly an important role for delaying the senescence of the cultivars with the senescent-sensitive type.
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