中文摘要：

以美棉33B为材料,于棉花中部果枝开花时进行干旱处理（土壤相对含水量由（75±5）%自然减少直至吐絮）,研究花铃期干旱对棉铃对位叶糖代谢及铃重的影响。结果表明,花铃期干旱处理,棉铃对位叶净光合速率降低,且中部降幅〉上部〉下部;棉铃对位叶可溶性糖含量下部和上部果枝增加而中部降低,蔗糖含量增加而淀粉降低,表明干旱促进叶片光合产物向蔗糖分配;棉铃对位叶蔗糖磷酸合酶、蔗糖合酶活性降低、酸性转化酶活性先降低后增加,且对中部和上部的影响大于下部,表明蔗糖合成受抑制,而其降解先抑制后促进,降低可供外运的蔗糖水平。干旱条件下铃重降低,中部降幅〉上部〉下部。因此,棉铃对位叶蔗糖合成减少和外运受抑制是花铃期干旱条件下铃重降低的蔗糖代谢基础。

英文摘要：

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 bolrs subtending leaf, respectively, and the decline range was MFB〉upper fruiting branch （UFB）〉lower fruiting branch （LFt3）. 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.