Genetic variations in embryo and endosperm weights, seedling growth parameters and alpha-amylase activity of the germinated grains in rice (Oryza sativa L.).

Abstract

This paper describes the relationships between embryo and endosperm weights and seedling growth parameters, the characteristics of seedling growth and the relationships of the seedling growth parameters with alpha-amylase activity in 36 rice cultivars belonging to three ecospecies, japonica, indica and javanica. The embryo weight was positively and significantly correlated with the endosperm weight in the javanicas, but not in the japonicas and indicas. The entries with the heavier embryo and endosperm weights developed larger top dry weights (TDWs) and leaf areas (LAs) in the javanicas, but not in the japonicas and indicas. Four cultivar groups were classified on a plane defined by the first and second principal components for the seedling growth parameters at different growth or sampling stages of the three ecospecies. The factor loadings of the growth parameters, i. e. top dry weight (TDW), leaf area (LA), relative growth rate (RGR), net assimilation rate (NAR) and top dry weight : leaf area ratio (TLR) varied with the growth or sampling stages of the three ecospecies. The first and second principal components included the different growth parameters depending on the growth or samplin* stages of the three ecospecies. However, the parent-offspring cultivars and the brewer's cultivars were found to belong to the same cultivar groups throughout the sampling or growth stages. Furthermore, some of the cultivar groups or cultivars developed high TDWs through the increase of RGRS and NARS together with the increase of LAS and TLRS at the different sampling or growth stages in the three ecospecies except for the japonicas at the second sampling or growth stage. In the laboratory experiments, the alpha-amylase activity was positively and significantly correlated with the shoot and root fresh weights 3 and 6 days after seed incubation in the japonicas and javanicas, and only nine days after seed incubation in the indicas. However, the laboratory performance of integrated alpha-amylase activity during nine days was not correlated with the glasshouse performance of the TDW and RGR in the three ecospecies. Instead, the principal component analyses indicated that one cultivar group displayed a high integrated alpha-amylase activity together with a high TDW 10 days after sowing and a high RGR at this stage in the japonicas and indicas. However, the cultivar groups with a high integrated alpha-amylase activity and RGR exhibited a low TDW in the javanicas.