Basic Study on Super Panicle Weight Type Varieties in Rice

研究了超穗型水稻品种小穗数、库容量和灌浆过程的特点。主要研究结果如下：1.高产半矮秆和中育稻SPWT具有较高的库容量，这是因为它们具有较高的每m^2小穗数和一粒体积(重量)小穗数，以及碳水化合物从营养器官到穗部的良好运输系统。穗上不同部位的最终粒重主要由籽粒灌浆速率与灌浆期的比较决定，而与包括SPWT在内的不同品种的籽粒大小差异不大。随着移栽至抽穗各阶段施氮量的增加，SPWT品种的谷壳变小，粒重变轻。容重越大的糙米粒重越大，粒重与糙米体积密切正相关，这主要与糙米的稠度有关。结实期籽粒成熟率和千粒重与灌浆期每粒的根系活力(α-萘胺氧化活力)呈极显著正相关，且随着根系活力的增加，这两个性状的促进作用在位于穗下部的下位小穗中表现得更明显。

This study was carried out to clarify the characteristics of determining processes of number of spikelets, sink capacity and grain-filling in super panicle weight type (SPWT) varieties in rice. The results obtained were summarized as follows ;1. The high yielding semidwarf and intermediate culmed indica SPWT varieties had higher sink capacity due to higher both components, i.e., number of spikelets per m^2 and 1 grain volume (weight) and good transportation system of carbohydrates from the vegetative organs to the panicle.2. The final grain weight at the different positions in a panicle was mainly determined by the grain-filling rate compared with the grain filling period, irrespective of large differences in grain size among varieties including SPWT.3. With increasing amount of nitrogen application at various stage from transplanting to heading decreased the hull size of SPWT varieties and resulted in lighter grain weight. The unhulled grains with heavier specific weight showed heavier grain weight, and the grain weight closely and positively associated with the volume of brown rice which was mainly related to the thickness.4. The percentage of ripened grains and 1000-grain weight of a SPWT variety were strongly and positively correlated with the root activity (α -naphthylamine oxidizing activity) per grain during grain-filling period, and the promotion of these characters with increasing the root activity were greater in the inferior spikelets located on the lower part of a panicle.