Coordination Between Photosynthate Transport And Boll Weight And Quality During Defoliation Ripening Of Cotton

Defoliation and ripening technology are an important prerequisite for cotton mechanical harvesting.It not only improves the picking efficiency and reduces the impurity content of mechanical harvesting,but also realizes the centralized boll opening,which is helpful to improve the quality of raw cotton.The application of defoliation ripening agent had a certain effect on the transport of photosynthetic products in various organs of cotton boll leaf system,cotton yield and fiber quality.Therefore,in this study,varieties（materials）with different sensitivity of defoliation agent and cotton boll morphology were selected,and different spraying time of defoliation ripening agent was set according to R_d/b value（the ratio of cotton boll age and boll stage when defoliation ripening agent was sprayed）,defoliation ripening agent was sprayed at different stages of Cotton Boll Development,and the differential changes of cotton boll weight and fiber quality under different defoliation ripening conditions were analyzed,Clarify the quantitative relationship between the damage amount of boll weight and fiber quality and the spraying time of defoliation and ripening,and clarify the ways that defoliation and ripening affect the transportation of photosynthetic substances and the coordinated improvement of boll weight and quality,so as to provide theoretical support for realizing the good defoliation and ripening effect of mechanically harvested cotton.The main results are as follows:1.Effect of defoliation and ripening on boll weight and fiber quality of cotton and appropriate spraying methodThe defoliation ripening agent and spraying time had a significant impact on the single boll weight and fiber weight.Spraying defoliation ripening agent had a significant impact on the single boll component,which was reduced by 0.24～0.59 g compared with the control.The fiber length was not significantly affected by defoliation ripening,which was only reduced by 0.67～0.86 mm compared with the control.The fiber specific strength was greatly affected by defoliation ripening agent,which was significantly reduced by2.48～3.32 c N·tex^-1,and the micronaire value was also significantly reduced by 0.74～0.97.When the R_d/bvalue is 0.52,the dry weight of single boll component decreases the most,and the breaking strength and micronaire value also decrease significantly.When the damage of single boll weight is controlled at 5%,the spraying time R_d/b of defoliation ripening agent should be 0.58～0.75;If the fiber weight damage is 2%,the spraying time R_d/b of defoliation ripening agent should be 0.77～0.82.2.Effect of defoliation and ripening on photosynthetic product transport and its coordinated relationship with boll weight and qualityThe effect of defoliation and ripening agents on boll transport was significantly reduced,and there was a positive linear correlation between single boll weight and fiber quality.For each 0.1 g increase in the transport capacity of bell shell,the single bell component increased by 0.08～0.13 g,and the breaking strength increased by 0.05～0.16 c N·tex^-1.The breaking strength increased by 0.14～0.18 c N·tex^-1 and the micronaire value increased by 0.05～0.07 for each 0.1 g increase in the transport capacity of single boll components.3.Judgment basis of spraying time for defoliation and ripening of mechanically harvested cotton in XinjiangThe judgment of spraying time of defoliation and ripening agent should be comprehensively considered in combination with climatic conditions,cotton variety characteristics and boll period.From the perspective of coordination between Boll Weight and fiber quality,if the decline of single boll weight is less than 5%,it is the risk time for cotton bolls to spray defoliation and ripening agent,that is,defoliation and ripening agent can be sprayed at 31 days of Boll age.If the fiber quality damage is controlled at 2%,it is the safe time for cotton bolls to spray defoliation ripening agent,that is,the boll age of 41 days can be sprayed.In cotton production,the defoliation and ripening agent is mainly Thidiazuron mixed with Ethephon,and the defoliation and ripening agent with 135 m L·hm^-2 effective ingredients containing thidiazuron and diuron and1350 m L·hm^-2 ethephon 40%water solution is used.Spraying at 40 days of cotton boll age is a safe spraying date to ensure better boll weight and fiber weight.