水稲の子実生産に関する物質生産的研究 : 第1報 出穂期前に貯蔵された炭水化物および出穂後の乾物生産が子実生産に及ぼす影響

抄録

The assimilation products reserved in rice grain during the ripening period is considered to consist of two parts. One part is the assimilate reserved in the rice plant until heading stage (C), which is transferred into the grains during the ripening period; the other part is the assimilate produced during the ripening period (ΔW). This study was carried out to elucidate the effect of these two parts on grain yield. Several long culm and short culm varieties of Japonica and Indica types cultivated in Japan, Taiwan and the U.S.A. were used (Table 1). Moreover, planting density, top- dressing and thinning treatments were conducted as shown in Table 2. The results obtained are summarized as follows: 1. The increase in ear weight during the ripening period (ΔE) showed significant positive multiple-correlation with ΔW and C. However, the correlation between ΔE and ΔW was significant only when the range of variation of C was very small. On the contrary, there was significant positive correlation between ΔE and C at any values of ΔW (Fig. 1). 2. When C/(C+ΔW) value was high, the assimilate was efficiently transferred into the grains (Fig. 2). 3. Both C and ΔW per grain increased the percentage of ripened grains, but C was more effective than ΔW in producting this increase. 4. The results mentioned above suggest that C influences the increase of ΔE by means of promoting of the accumulative ability of the assimilation product in grain. Therefore, the increase of C is very important for high grain yield. 5. The range of variation of C differed more according to varieties than cultivation conditions, and C in recently improved varieties was larger than in the old varieties (Table 3 and Table 4).