The remobilization of non-structural carbohydrates stored in the capsule wall can mitigate cotton fiber strength damage caused by harvest aids.

The remobilization of stored assimilates in the capsule wall following the application of harvest aids significantly contributes to boll weight formation. However, the impact of remobilized non-structural carbohydrates (NSC) from the capsule wall on fiber strength development remains unclear. In this study, conducted during the late growth stage of cotton, we investigated how the remobilization of NSC in the capsule wall affects fiber sucrose metabolism and fiber strength after applying harvest aids. Our results indicate that within 1-7 days post-applying, starch enzyme activity in the capsule wall increased by 2.78-14.78 %, leading to enhanced remobilization of stored NSC for fiber development. This maintained a cellulose accumulation rate of 5.17-2.73 mg g d, ensuring a fiber strength increase of 0.16-0.26 cN tex d. By the time of boll opening, fiber strength had increased by 2.37-2.50 cN tex compared to pre-application. Specifically, for every 0.1 g of NSC remobilized from the capsule wall, fiber strength increased by 1.13-1.15 cN tex. These findings suggest that the remobilization of stored assimilates in the capsule wall supports sustained cellulose accumulation, thereby mitigating potential damage to fiber strength caused by harvest aids. Therefore, enhancing amylase activity in the capsule wall to promote NSC remobilization is an effective strategy for improving fiber strength under harvest aid application.