Effects of Drought on the Sucrose Metabolism of Subtending Leaves of Cotton Bolls at Different Fruiting Branches and Boll Weight during Flowering and Boiling Stages
This study aimed to illustrate the mechanism of sucrose metabolism in subtending leaves of cotton bolls and its relationship with boll weight under drought stress during flowering and bolling stages.The 2-year-long experiments were conducted using pools of upland cotton (Gossypium hirsutum L.) plants,NuCOTN 33B,subjected to drought stress (relative water content reduced naturally until the boll opening stage) on the day of anthesis of the middle fruiting branches (MFB),using well-watered conditions as the control.The net photosynthetic rate declined under drought stress in the boll's subtending leaf,respectively,and the decline range was MFB＞upper fruiting branch (UFB)＞lower fruiting branch (LFB).Drought stress increased the soluble sugar contents of subtending leaves at LFB and UFB but decreased them at MFB.Sucrose content was increased and starch content decreased concomitantly,indicating that drought facilitated the partitioning of photosynthate into sucrose.Drought stress also depressed the activities of sucrose phosphate synthase and sucrose synthase,while acid invertase activity was initially decreased and then increased.The changes of MFB and UFB exceeded those of LFB,indicating that sucrose synthesis was inhibited,the degradation was first inhibited then promoted,causing a reduction in the amount of sucrose available for export.As a result,the boll weight declined during drought,and the decline range was MFB＞UFB＞LFB.In conclusion,the decreased sucrose synthesis and the impaired sucrose efflux of subtending leaves of bolls were the main causes for decreased boll weight under drought conditions during flowering and bolling stages of cotton.
cotton (Gossypium hirsutum L.)flowering and bolling stagedroughtsubtending leaves of bollssucrose metabolismboll weight
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