Comparative Studies on Dry Matter Production, Plant Type and Productivity in Soybean, Azuki Bean and Kidney Bean : I. Differences in dry matter accumulation patterns under the low population density

Abstract

The object of this study is to investigate the differences in dry matter production, plant type and productivity in soybean (Glvcine max Merr.), azuki bean (Vigna angularis) and kidney bean (Phaseolus vulgaris L.). For the first trial of this study, dry matter accumulation patterns of three crops including twelve varieties were compared under the low population density (60cm × 45cm, singling). The results obtained were summarized as follows: 1. Varietal differences in dry weight of vegetative portion were cleared up after about the initiation of flowering in each crop. Indeterminate types of soybean and kidney bean, and late varieties of azuki bean produced more vegetative matter than determinate and early ones. 2. The distribution ratio of dry matter to leaves was the highest in the early growth stage and gradually declined with time in all varieties. However, some of them were found to show a peak at the initiaI branch-elongation stage just before the flowering. 3. The distribution of dry matter produced during the overlapping period of vegetative and reproductive growth were closely related with the degree of determinancy and earliness; the distribution ratios (%) into vegetative portion were higher in indeterminate and late varieties than in determinate and early ones, and those into reproductive portion indicated the opposite relation with vegetative one. 4. In azuki bean there were little differences in number of leaves and dry weight on main stem among varieties. Varietal differences of total dry matter weight (g/pl.) which were heavier in late varieties resulted mainly in the differences in branches. Main stem ratios (main stem/main stem+branches, %) in dry weight wcre lower in late varieties, especially in viny types. 5. Two peaks of net assimilation rate (NAR) appeared in some varieties of each crop. One occurred at the initial branch-elongation stage in each crop, the other at young pod stage in soybean and at pod filling stage in azuki bean. The patterns of relative growth rate (RGR) were similar to those of NAR, and the peaks were more remarkable in RGR. In kidney bean, values of NAR of indeterminate types decreased rapidly after the flowering. 6. At the initial branch-elongation stage, NAR was corrclated positively, but not significantly, with the distribution ratio of dry matter to leaves (r=0.85) in kidney bean. NAR also indicated positive and significant correlations with the pod growth rate (r=0.83) and the distribution ratio into pod (r=0.95) of main stem at pod filling stage in azuki bean. 7. Grain yield per plant was positively correlated with the growth period, number of node per plant and maximum leaf area. Grain weight per maximum leaf area (g/m2) was, however, lower in indeterminate types than in determinate ones in kidney bean.