Effects of Planting Date on Sucrose Metabolism in the Leaf Subtending to Cotton Boll,Within-boll Yield Components and Fiber Quality

[Objective] The present study aimed to investigate how sucrose metabolism in the leaf subtending to cotton boll, within-boll yield components and fiber quality respond to varying planting dates. [Method] Two upland cotton lines A705 and A201 differing in cotton boll traits were field tested in 2016-2017. Two different planting dates were designed with early planting on April 12, 2016, and April 15, 2017, and late planting on May 6, 2016, and May 28, 2017, respectively. Dynamics of non-structural carbohydrates (sucrose, hexose, starch) and key sucrose metabolism enzymes in the leaf subtending to cotton boll were examined including vacuolar acid invertase, cell wall acid invertase, sucrose phosphate synthase and sucrose synthase. The differences between two planting dates were compared for within- boll yield components, fiber quality and sucrose metabolism related characteristics. [Result] Late planting lengthened the period of cotton boll maturation relative to early planting. Boll weight, seed mass per boll, seed index and fiber length were increased, and lint percentage and micronaire were decreased. Late planting reduced the activities of cell wall acid invertase and sucrose synthase responsible for sucrose degradation, and in turn led to the increment of sucrose concentration in the subtending leaves which might enhance the carbon supply to the opposite bolls. [Conclusion] Lower temperature due to late planting could contribute to the more full development of cotton bolls. Late planting is an alternative consideration in improvement of fiber quality in cotton cultural practices.