Abstract:

The objective of this study was to investigate the boll development and the boll-leaf photosynthetic products transportation and allocation. Using two cotton cultivars, one with conventional fiber quality (Sumian 15), another with high fiber quality (Kemian 1) at Key Laboratory of Crop Genetics and Physiology of Jiangsu Province, Yangzhou University, China during the 2004 and 2005 growing seasons.
Two treatments of cutting top of main stem and all fruiting branches to decrease the boll sink, and three treatments of cutting off different ratio of each leaf in whole plant to restrict the boll development were designed.
In comparison with the control, in deceasing boll sink treatment, the boll volume increased and the boll weight enhanced. The leaf soluble sugar content and starch content increased by 41.0% and 4.1% respectively for Kemian 1, by 14.8% and 77.3% for Sumian 15 respectively at 40 days post-anthesis(DPA). The ¹⁴C assimilates exportation rate from leaf increased too, with 17.6% and 6.8% for Kemian 1 and Sumian 15 respectively at 24 h after labeling in 30 DPA. The ¹⁴C assimilates importation rate to boll enhanced, with 13.7% and 10.1% for Kemian 1 and Sumian 15 respectively. The total N and soluble sugar contents in phloem sap also increased for the two different cultivars. Compared with the control, in insufficient leaf source treatment, the boll volume decreased and the boll weight reduced. In the treatment of cutting 3/4 leaves area, the leaf soluble sugar content and starch content decreased by 1.36 mg g^-1 and 2.69 mg g^-1 respectively at 40 DPA for Kemian 1, by 3.69 mg g^-1 and 3.05 mg g^-1 respectively for Sumian 15. The exportation and importation rates of ¹⁴C assimilates decreased, especially for Sumian 15. The contents of total N and soluble sugar in phloem sap also decreased for the two cultivars. These results suggest that effective technique should be used to enhance the boll development by transporting more assimilates from leaves to bolls, enhancing the boll weight, and laying a good foundation for higher yield.

Key words: Cotton, Source-sink regulation, Boll, Transportation and allocation