Abstract: To elucidate the relationship between ethylene evolution from the grains and the appearance quality of rice, ten rice genotypes were used to deterimine the ethylene evolution rate, 1-aminocylopropane-1-carboxylic acid (ACC) concentration and appearance quality of rice, and the effects of chemical regulators on concentrations of ethylene and ACC were also investigated to verify the roles of ethylene in rice quality. The ethylene evolution rates and ACC concentrations in grains during the mid and late grain filling stages were very significantly and positively correlated with chalky kernel percentage and chalkiness of rice. The varieties with a low ACC concentration in grains exhibited a close amyloplast arrangement and small gap between starch granules, whereas those with a high ACC concentration in the grains showed a loose arrangement and wide gap between the granules. Application of 1 μmol/L ACC to panicles at mid and late grain filling stages significantly loosened amyloplast arrangement and increased chalky kernel percentage, chalky area and chalkiness of rice, and the results were reversed when 1 μmol/L amino-ethoxyvinylglycine, an inhibitor of ACC synthetic enzyme, was applied to panicles. A practice of moderate dry-wet alternate irrigation reduced ethylene evolution and ACC concentration in grains and thereby reduced chalkiness. The results suggested that ethylene and ACC in grains played an important role in the endosperm structure and appearance quality of rice, and the appearance quality would be improved by reducing ethylene and ACC concentrations in grains either through variety breeding, or chemical regulations or cultivation techniques.

Key words: rice, ethylene, 1-aminocylopropane-1-carboxylic acid, amyloplast structure, appearance quality, dry-wet alternate irrigation

摘要： 为阐明水稻籽粒乙烯与稻米外观品质的关系，试验采用10个不同基因型的水稻材料，测定了结实期籽粒乙烯释放速率、1氨基环丙烷1羧酸（ACC）浓度和稻米的外观品质，分析了它们之间的关系并用化学调控等方法进行验证。结果表明，灌浆中后期籽粒乙烯释放速率和ACC浓度与稻米的垩白粒率和垩白度均呈极显著的正相关。籽粒中ACC浓度低的品种，胚乳淀粉体排列紧密，间隙较小；而籽粒中ACC浓度高的品种，淀粉体排列疏松，间隙大。在灌浆中后期分别用1 μmol/L ACC 处理稻穗，稻米的淀粉体排列变疏松，垩白粒率、垩白大小和垩白度均显著增加，用1 μmol/L氨基乙氧基乙烯基甘氨酸（ACC合成酶抑制剂）处理稻穗，结果则相反。结实期进行轻干湿交替灌溉，降低了籽粒乙烯释放速率、ACC浓度和垩白度。说明籽粒中乙烯和ACC对稻米胚乳淀粉结构和外观品质起重要的调控作用，通过品种选育、化学调控和灌溉等措施降低籽粒乙烯释放速率和ACC浓度，可以改善稻米的外观品质。

关键词: 水稻, 乙烯, 1-氨基环丙烷-1-羧酸, 淀粉体结构, 外观品质, 干湿交替灌溉