中文摘要：

以水稻品种武育粳3号（粳稻）和扬稻6号（籼稻）为材料,研究了结实期土壤水分和灌溉方式对产量、米质、籽粒中淀粉合成关键酶活性和内源乙烯释放速率的影响及它们之间的关系。结果表明,与WW（保持水层,well-watered）或CI（常规灌溉,conventional irrigation）相比,土壤轻度落干（MD,moderate soil-drying,土壤水势保持在-10～-30kPa）和轻干湿交替灌溉（W-MD,alternate wetting and moderate-drying irrigation,土壤落干至土水势为-25kPa时复水）显著提高了千粒重、稻米的最高黏度和崩解值,显著降低了垩白度和消减值;土壤干旱（SD,severesoil-drying,土壤水势保持在-40～-60kPa）和重干湿交替灌溉（W-SD,alternate wetting and severe-dryingirrigation,土壤落干至土水势为-50kPa时复水）则使稻米品质变劣。MD和W-MD处理显著降低了籽粒乙烯释放速率,增加了灌浆中后期籽粒中蔗糖合酶（SuS）、腺苷二磷酸葡萄糖焦磷酸化酶（AGP）、淀粉合酶（StS）和淀粉分支酶（SBE）活性,SD和W-SD处理则提高了籽粒内源乙烯释放速率,降低了上述各酶的活性。说明结实期土壤轻度落干或轻干-湿交替灌溉可以改善稻米品质,籽粒SuS、AGP、StS和SBE活性的增强和内源乙烯水平的降低是稻米品质改善的重要生理原因。

英文摘要：

The objective of this study was to investigate whether a moderate soil-drying or an alternate wetting and moderate-drying irrigation during the grain filling period could improve the grain quality and increase yield in rice. Two rice cultivars, Wuyujing 3 （japonica） and Yangdao 6 （indica）, were grown in pots and cement tanks. Three soil moisture treatments and three irrigation patterns, well-watered （WW, well-watered） and conventional irrigation （CI, continuous flooding）, moderate soil-drying （MD, soil water potential at - 10 - - 30 kPa） and alternate wetting and moderate-drying irrigation （W-MD, re-watered when soil water potential reached at - 25 kPa）, and severe soil-drying （SD, soil water potential at - 40 - - 60 kPa） and alternate wetting and severe-drying irrigation （W-SD, re-watered when soil water potential reached at - 50 kPa）, were imposed during grain-filing. Compared with WW or CI, MD or W-MD significantly increased grain weight, peak viscosity, and breakdown values, and reduced chalkiness and setback values. The results were reversed for SD or W-SD treatments. Activities of sucrose synthase （SuS）, adenine diphosphoglucose pyrophosphorylase （AGP）, starch synthase （StS）, and starch branching enzyme （SBE） in grains in middle and late grain-filling stages were significantly enhanced, whereas ethylene revolution rate of grains decreased, under MD or W-MD. The SD or W-SD had the opposite effects. The results indicate that both MD and W-MD can improve rice quality, resulting from the physiological mechanism of enhancing activities of SuS, AGP, StS, and SBE and decreasing ethylene production in grains.