Effects Of Drought And Water Replenishment In Summer Cotton Boll Stage On Yield And Quality Of Cotton Bud Shedding

The aim of this thesis is to study the effects of summer drought on summer cotton production,especially the development of cotton during the bolling period.A random block design was adopted to set up two water treatments: drought and replenishment.Drought stress was realized by limiting irrigation during the boll reneging period,and then replenishment treatment was carried out until the soil moisture content reached a certain level.The difference between the two treatments was compared by measuring cotton boll shedding rate,yield,fiber quality,average length of top half,uniformity index,Macron value,breaking strength and growth rate,etc.The results are as follows:(1)Drought stress significantly increased the rate of boll shedding and decreased the cotton yield and fiber quality,while water replenishment significantly decreased the rate of boll shedding and increased the cotton yield and fiber quality.In particular,water replenishment had a great effect on fiber quality,which showed that the average length,average length,uniformity index,Macron value,break strength and growth rate of the upper part of the fiber were significantly higher than those of the control group without stress.In addition,the study also found that there was a significant negative correlation between cotton boll shedding rate and cotton yield and fiber quality,indicating that the higher the boll shedding rate,the lower the yield and fiber quality.These results provide a basis for producers to develop effective irrigation management strategies in arid summer environments.(2)Under drought stress,chlorophyll content and relative water content of leaves decreased significantly,while MDA,free proline and soluble protein contents increased significantly.Meanwhile,SOD activity was significantly increased under drought stress,indicating that cotton was affected by oxidative stress.In addition,drought stress time also had significant effects on POD and CAT activities.These results indicated that drought stress had a significant negative effect on cotton growth and development,and affected the oxidative stress response and metabolism of cotton.(3)The expressions of SUSY,Inv1 and Inv2 genes related to sucrose synthesis were regulated under drought stress.In addition,cellulose synthesis-related genes DR455875 and ES801059 were also affected by drought stress.Water treatment can reverse the expression trend of these genes,so as to effectively improve cotton yield and fiber length.Taken together,the results highlight the negative effects of drought stress on cotton production,especially during the bolling period.At the same time,the importance of water replenishment to alleviate the negative effects of drought stress on cotton production was expounded.These findings provide valuable information that can be used to develop effective drought stress control strategies to ensure the sustainability of cotton production in drought-prone areas.