Studies on Productivity of Rice Plants Growing the North-Marginal Area in Japan : II. Influence of cool-weather damage on yield and harvest index

[摘要] In the present paper, varietal differences in yield and harvest index were studied. The results obtained were summarized as follows; 1. Rice plants suffered from cool-summer damage due to floral impotency in 1982, and suffered from cool-summer damage due to delayed growth in 1983. The mean yield among varieties was 358.9 kg/10a in 1982 and 82.8 kg/10a in 1983 (Table 1). Grain yield (Y) was correlated significantly with harvest index (HI), but Y had no significant correlation with dry matter production during the whole growth period (ΔW) (Fig. 1). 2. HI can be expressed by the following identical equation ; HI=Y/ΔW = N/(LAD) × (KW)/((ΔW/(ΔIS))) × (RP)/(ΔTS) × 1/((MEi/LAD)) where N is number of grains; LAD is leaf area duration; KW is 1000-kernel-weight; ΔIS is accumulated solar radiation intercepted by the canopy; RP is percentage of ripened grains; ΔTS is accumulated solar radiation; MEi is mean value of the efficiency for intercepting solar radiation. Correlation coefficients, simple and partial, of HI with it's components were shown in Table 2. HI was significantly correlated with RP/ΔTS and KW/(ΔW/ΔIS) in simple correlation, but significantly correlated with all components in partial correlation (Table 2). 3. Percentage of ripened grains (RP) can be expressed by the following identical equation; RP=(RN)/N=(FN)/N×(RN)/(FN) where RN is number of fully ripened grains that were selected with 1.06 specific gravity; FN is number of fertilized grains. High significant correlation was found between RP and FN/N (fertility percent) in 1982. On the other hand, highly significant correlation was found between RP and RN/FN (percentage of fully ripened grains to fertilized grains) in 1983 (Fig. 2). 4. In 1983, RN/FN was correlated significantly with accumulated daily mean temperature (AT) and accumulated solar radiation (AS) from heading date to October 7. (RN/FN)/(AT-400) was correlated significantly with light diminution coefficient (K') and rate of indecomposable chlorophyll at milk-ripe stage (C), but it had no significant correlation with the efficiency for solar energy conversion after full heading stage (Ec2)(Fig. 3, Table 3).

[学科分类] 农业科学（综合）