Effects of Removing Basal Fruiting Branches on Cellulose Accumulation and Activities of Cellulose Synthesis-Related Enzymes in Cotton

Using cotton cultivar that undergoes premature senescence in the late stage of growth, we studied the effects of removing two basal fruiting branches of two cotton varieties, namely, Quanyin-2 and Jiza-999, on the leaf area index, the SPAD value of leaf subtending cotton boll, and the development of cotton fiber in the late stage of cotton growth. We focused on the differences in cotton cellulose accumulation and fiber-related enzyme activities after removal of the basal fruiting branches and the development of cotton fiber during premature senescence. The results showed that removing the basal fruiting branches can maintain the green leaf area of the cotton canopy and the SPAD value of the subtending leaf during the late stage of reproductive growth. The period of rapid accumulation of fiber cellulose lasted longer in plants from which the basal fruiting branches had been removed, and the beginning and end of the rapid accumulation period was later than in the control group with premature senescence. The activities of cellulose synthesis-related enzymes (sucrose phosphate synthase, sucrose synthase, β-1,3-glucanase, and invertase) were higher in plants in which the basal fruiting branches had been removed than in the control group after 10 days post-anthesis. Removing the basal fruiting branches can optimize the accumulation of cellulose in cotton boll during the late growth stage and mitigate the effects of premature senescence on cellulose synthesis. We found that the peak values for cotton fiber development-related enzyme activities in the control group occurred earlier, which tended to bring cotton fiber development forward and negatively impacted fiber yield.