Abstract: Cotton is one of important cash crops, but so far, few studies on the boll and leaf system at the same node position in cotton were reported. In this study, the effects of source/sink ratio on growth and development and physiological characteristics in cotton were evaluated using CCRI29, a BT-transgenic hybrid cotton cultivar. Three treatments were designed in the experiment: picking off buds on the fruit branch at 8 d after anthesis for leaving two or three leaves to support one boll (PB), picking off some leaves on the fruit branch at 8 d after anthesis for leaving one leaf to support two bolls (PL), and normal training managements (CK). The results indicated that in PB treatment, the content of soluble protein increased and the chlorophyll content in the later growth stage boosted in middle and lower fruit branch leaves, prolonging the function period of the leaves. In PL treatment, the chlorophyll content of leaves was promoted in the earlier growth stage, and decreased sharply in the later growth stage, and the soluble protein content of leaves was the lowest among the three treatments, suggesting that there was a temporarily physiological compensation effect in fruit branch leaves, but the leaf senescence was accelerated by cutting leaves at late growth stage. Altered the ratio of source/sink also affected the SOD and POD activities and MDA content in fruit branch leaves, showing a tendency that both increasing and decreasing source/sink ratio could reduce the activities of SOD and POD. The MDA content of leaf under different treatments was ranked as PL>CK>PB. The results of statistic analysis indicated that there were a significant, positive correlation between SOD activity and POD activity ( r = 0.845**, P < 0.01) in CK treatment, but no correlation between SOD and POD activities after changing the source/sink ratio, indicating that the ratio of source/sink affected the physiological characteristics and function period of fruit branch leaves in cotton. As a result of changing source/sink ratio, the ringle boll weigh was PB>CK>PL.

Key words: Cotton, Source-sink ratio, Fruit-branch leaf, Physiological activity