水稻结实期不同粒位籽粒相关内源激素含量和关键酶活性的差异及其与品质的关系

 【目的】研究灌浆期水稻穗上不同粒位籽粒内源激素含量和关键酶活性的差异及其与籽粒品质形成的关系。【方法】以中熟籼稻扬稻6号和中熟粳稻扬粳9538为材料，按照一次枝梗数将稻穗分为上、中、下三个部位，以穗中部一、二次枝梗不同粒位籽粒为研究对象。【结果】灌浆前期开花较早的籽粒中玉米素（Z）+玉米素核苷（ZR）、吲哚乙酸（IAA）、脱落酸(ABA)含量以及淀粉合成酶（SSase）、淀粉分支酶（Q酶）活性明显高于同枝梗上开花较迟的籽粒，灌浆后期则相反；籽粒开花越早，其内源激素含量以及酶活性到达最大值的时间越早，峰值也越高。灌浆前期ABA、Z+ZR、IAA含量、ABA/（Z+ZR+IAA）比值以及SSase酶和Q-酶活性与千粒重、直链淀粉累积速率、直链淀粉含量呈显著或极显著正相关，与垩白度呈显著或极显著负相关，灌浆后期则相反；灌浆前期SSase和Q-酶活性与胶稠度呈负相关，中、后期则相反；与粗蛋白含量的相关两品种存在差异，与整精米率相关不显著。【结论】灌浆期水稻穗上不同粒位籽粒内源激素含量与关键酶活性存在差异；不同粒位间籽粒米质差异的形成与籽粒内源激素含量与关键酶活性密切相关。

Difference in Hormonal Content and Activities of Key Enzymes in the Grains at Different Positions on a Rice Panicle During Grain Filling and Their Correlations with Rice Qualities

Little is known the roles and mechanisms of hormones and key enzymes in the formation of the quality of grains at different positions within a rice panicle. This study investigated if the hormones in the grains are related with rice quality. Two rice cultivars, Yangdao 6 (indica) and Yangjing 9538 (japonica), were field-grown. All primary branches on a panicle were evenly divided into three parts of the upper, middle and basal. The grains were numbered as 1 to 6 on a primary branch and 1 to 3 or 4 on a secondary branch from the top to base. The results showed the contents of zeatin (Z) + zeatin riboside (ZR), indole -3- acetic acid (IAA) and abscisic acid (ABA) and activities of starch synthase (SSase), starch branching enzyme (Q-enzyme) in earlier-flowered grains were obviously greater than those in later-flowered grains at early filling stage, it was reversed at late filling stage. The earlier the spikelets flowered, the shorter the time reaching the maximum grain-filling rate (Vmax) was, the higher the contents and activities were. The contents of Z + ZR, IAA and ABA, the ratio of ABA to IAA+Z+ZR, and activities of SSase and Q-enzyme at early grain filling stage were positively and significantly or very significantly correlated with 1000-grain weight, amylose accumulation rate and amylose content, but negatively and significantly or very significantly correlated with chalkiness degree, the results were reversed at late grain filling stage. Activities of SSase and Q-enzyme at early grain filling stage were negatively correlated with Gel consistency (GC), whereas positively correlated with GC at mid and late grain-filling stages. The correlation of the hormones and enzymatic activities with crude protein content varied with cultivars, and the correlation with head milled rice rate was insignificant.