水稻穗上不同粒位籽粒胚乳结构及其结实期灌溉方式对它的调控作用

为探明水稻穗上不同粒位胚乳结构形成特征及结实期灌溉方式对它的调控作用, 本研究以籼稻扬稻6号和粳稻武运粳24为材料, 运用扫描电镜观察了穗上不同部位籽粒胚乳结构的形成动态。自抽穗至成熟设置保持浅水层(CK)、轻干-湿交替灌溉(WMD)和重干-湿交替灌溉(WSD) 3种灌溉方式, 观察了干湿交替灌溉方式对水稻产量和籽粒胚乳结构的影响。结果表明, 灌浆过程中稻米胚乳结构的形态建成顺序是, 上部穗籽粒早于中部穗籽粒更早于下部穗籽粒, 一次枝梗籽粒早于二次枝梗籽粒, 穗上早开花的籽粒早于迟开花的籽粒。与CK相比, 结实期WMD可以明显提高水稻产量; 其穗下部籽粒胚乳的淀粉体排列更紧密, 籽粒背部淀粉粒嵌挤甚至粘连。在WSD下, 稻米胚乳淀粉体排列疏松, 体积减小, 粒径差异增大, 相互间隙增大。灌溉方式对胚乳结构的影响, 因粒位而异, 以下部穗二次枝梗籽粒的腹部最为显著。表明水稻穗上不同部位籽粒胚乳结构形成与花后天数有密切关系; 结实期WMD可以改进穗下部籽粒胚乳结构, WSD则会使胚乳结构变差。灌浆期土壤水势-20 kPa 可作为改善稻米胚乳淀粉结构的节水灌溉低限指标。

Endosperm Structure of Grains at Different Positions of Rice Panicle and Regulation Effect of Irrigation Regimes on It during Grain Filling

In this study, an indica cultivar Yangdao 6 and a japonica cultivar Wuyunjing 24 were used to observe the changes in endosperm structure of grains at different positions of panicle with scanning electron microscope. Three irrigation treatments, namely shallow water layer (CK), alternate wetting and moderate drying (WMD), and alternate wetting and severe drying (WSD), were designed to investigate the effect of irrigation regimes on grain yield and grain endosperm structure. The endosperm structure formation in grains was earlier at the upper part of panicle than at the mid part of panicle, and earlier than at the lower part of panicle; the formation was earlier on a primary branch than on a secondary branch, and earlier in superior grains than in inferior grains. Compared with CK, WMD significantly increased grain yield. The starch granule in endosperm of grains at the lower part of panicle showed more compact arrangement, and that in the back part of grains was more crowded and even more adhered each other under WMD than under CK. Under WSD, the endosperm structure in grains showed that the starch granule arrangement was looser, the granule volume was decreased, and the differences in granule size and the gap between granules were increased, relative to those under CK. The effect of irrigation regimes on endosperm structure varied with grain positions, which was the most significant on the belly of grains at the secondary branch located at the lower part of panicle. The results suggest that the formation of endosperm structure in the grains at different parts of panicle is closely related to days after anthesis. WMD may improve, whereas WSD deteriorate, the endosperm structure of grains at the lower part of rice panicle. Soil water potential -20 kPa can be used as the low limit of soil water potential index in the water-saving irrigation for improving endosperm structure in grains during the grain filling period of rice.