暖地における水稲品種の物質生産に関する研究 : 第2報明治期以降の新旧品種の子実生産特性

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In a previous paper, we have shown that no difference in total dry matter weight per area at harvest was observed between old (ear-weight type) and new (ear-number type) types of cultivars, but that the new types produced less dry matter before heading and more dry matter after heading than the old ones. It was considered that this difference in dry matter increase between both types could affect directly the yield components which were determined at various growth stages. The present investigation was carried out to analyse the chronological changes in the characteristics of grain production in comparison of old types with new types of cultivars. Attempts were also made to compare cultivars in the warmer part of Japan with those in the cooler part (northern area of Japan) which has the reputation of being a high yielding area. Grain yield was higher in the new types than in the old types of cultivars. Grain yield was more closely correlated to the harvest index (r=0.919^<***>) than to the total dry matter weight (r=0.630^<N.S.>) (Fig. 1). There was no difference in sink capacity, defined as spikelet weight with the exclusion of grain per area at harvest, between old and new types of cultivars (Table 1). The new types produced more dry matter as compared with their sink capacity, suggesting that their sink capacity is small (Figs. 2 and 3). The enlargement of leaf area which was caused by the increase in sink capacity was more pronounced in rice plants growing in the warmer part than in the cooler part of Japan (Figs. 4 and 5). This phenomenon could be ascribed to two factors, firstly the temperature which is higher in the warmer part of Japan, secondly the fact that the new types in the warmer part had fewer spikelets per ear and a larger increase in ear number per area than those in the cooler part (Figs. 8, 9 and 10). Consequently, the new types had a lower sink/source ratio in the warmer part (Fig. 5). Here, sink/source ratio was defined as the ratio of sink capacity to leaf area at heading. But the old types of cultivars had still a higher sink/source ratio than the new types (Fig. 5). In contrast, in the cooler part of Japan, the sink capacity was adequate. Also, due to the higher number of spikelets per ear in addition to a small leaf area index, the sink/source ratio has tended to increase lately (Figs. 4 and 8). From these results, it appears that the sink capacity of rice plants growing in the warmer part of Japan should be higher to achieve further increase in grain yield. However, the increase in the sink capacity would be very difficult to achieve since new types of cultivers with many and small ears require heavy nitrogen and high planting density. Then, in these types the leaf area becomes readily enlarged, excessive growth would result. Therefore, it would be desirable to breed cultivars with high sink capacity but without excessive growth.
日本作物学会の論文
1984-03-05

暖地における水稲品種の物質生産に関する研究 : 第2報明治期以降の新旧品種の子実生産特性

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暖地における水稲品種の物質生産に関する研究 : 第2報 明治期以降の新旧品種の子実生産特性

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暖地における水稲品種の物質生産に関する研究 : 第2報明治期以降の新旧品種の子実生産特性