中文摘要：

以扬稻6号和武育粳3号为材料，研究了结实期干-湿交棒处理对稻米品质的影响及其机理。结果表明．结实期轻度干-湿交替处理改善了稻米的加工品质和外观品质，提高了米粉的崩解值，降低了消减值，而重度干-湿交替处理结果则相反。轻度干-湿交替处理还提高了籽粒中蔗糖合酶（SuSase）、ADP葡萄糖焦磷酸化酶（ADPGase）、可溶性淀粉合酶（SSSase）和淀粉分支酶（Q酶）的活性。重度干湿交替处理则降低卜述酶类的活性。上述酶类活性与稻米主要品质指标显著相关。根系伤流中1-氨基环丙烷-1羧酸（ACC，乙烯合成前体）浓度、籽粒中ACC浓度和乙烯释放速率在轻度干-湿交替处理条件下均明显降低，而在重度干湿交替处理条件下则明显提高。根系伤流中ACC浓度、籽粒中ACC浓度和乙烯释放速率与suSase、ADPGase、SSSase和Q酶活性呈显著或极显著负相关。灌浆结实期土壤水分处理改变了根系ACC浓度，影响了籽粒乙烯释放速率和ACC浓度，进而影响籽粒蔗糖-淀粉代谢途径关键酶的活性，最终影响了稻米品质的形成。

英文摘要：

The effect of dry-wet alternate water treatment during grain filling on grain quality and its physiological mechanisms were investigated with Yangdao 6 （indica） and Wuyujing 3 （japonica） as materials. The results showed milling quality and appearance quality were improved, breakdown values of rice flour were increased and setback values were decreased under alternate moderate drying and wetting treatment （MD）. The results were reversed under alternate severe drying and welling treatment （SD）. The activities of sucrose synthase （SuSase）, ADP glucose pyrophosphorylase （AI）PGase）, soluble starch synthase （SSSase）, and Q enzyme in grains increased under MD during grain filling, while decreased under SD. The enzyme activities were significantly correlated with main indices of grain quality. The concentrations of 1-aminocylopropane-l-carboxylic acid （ACC, biosynthetical precursor of ethylene） in root bleeding, the concentration of ACC and ethylene evolution rate in grains were significantly decreased under MD, while significantly increased under SI）. The concentrations of ACC in root bleeding, the concentration of ACC and elbylene evolution rate in grains were significantly or extremely significantly and negatively correlated with the activities of SuSase, ADPGase, SSSase and Q-enzyme. The shifting concentration of ACC in root under alternate drying-wetting treatment during grain filling affected the concentration of ACC and ethylene evolution rate in grains, which influenced the activities of enzymes involved in starch synthesis, and grain quality finally.