Comparison on the Yield and the Production and Distribution of Dry Matter in Rice between Crop Seasons

本試驗於1981年二期作與1982年一期作分別在屏東與臺中二地區進行，在水稻生育期間測定不同器官內乾物質、全氮及非構造性碳水化含物（TNC）含量的變化，以明瞭品種間、區域間與期作間產量差異的原因。 水稻抽穗時之全株乾物重以一期作為高，其中以屏東區臺農67號差異最為明顯，臺中地區臺農67號及臺南5號的差異較小。二期作稻抽穗期全株乾物重低落原因主要受分蘖數較少的影響，就單一分蘗平均乾重進行比較，反以二期作稍高。抽穗後穀粒發育期間乾物質的生產量，亦以一期作顯著優於二期作，屏東地區的差別最為明顯。 一期作水稻抽穗時莖稈內江NC濃度顯著高於二期作，抽穗期營養器官內TNC含量為二期作之1.5-5.5倍，表示有較多的預貯物質。抽穗後穀粒充實期間，屏東、臺中二地區之一期作TNC生產量高於二期作。非構造性碳水化合物收穫指數(HTNCI)均高，介於0.93-0.98之間，無地區、品種或期作性差異。而產量經由預貯物質而來的百分比（Pre-heading storage contribution)，一期作介於17.8-22.5%之間，二期作為11.6-17.9%。 葉片為水稻植株內含氮濃度較高之器官，屏東、臺中二地區於抽穗期葉片氮濃度表現不一致，但屏東區臺農67號葉片內氮濃度明顯的以一期作為低，和一期作極高產與二期作低產的表現，可推知抽穗期葉片內全氮濃度的高低與產量問的關係並不單純，植株的全氮收穫指數(HNI)以一期作為高，介於0.70-0.81之間，二期作為0.65-0.76，顯示前者有較多的轉流量，氮代謝作用與碳代謝作用之間可能互為影響，值得進一步研究。 期作間產量差異比較發現，千粒重差別不大，每穗穎花數與結實率乘積在期作間亦相似，穗數為決定產量的最主要因子。二期作低產除了穗數較少及抽穗時乾物重與TNC含量較低外，穀粒充實期間乾物質淨生產量亦較低，為今後謀求二期作水稻增產應注意的方向。 Two rice cultivars, Tainung 67 and Tainan 5, were grown in either Pingtung or Taichung area in the second crop of 1981 and first crop of 1982. Dry weight and contents of total nonstructural carbohydrates (TNC) and total nitrogen (N) in different plant fractions were detennined at stages of grain-filling. The purpose of this study was to investigate the causes of yield difference due to location, varietal or seasonal factors. Dry weight per hill at heading was consistently higher for the first than for the second crop. The difference was most significant for rice grown in Pingtung area. The lower dry weight of the second crop rice was due mainly to the fewer number of tillers per hill. Results showed that on a per tiller basis, the second crop rice possessed higher dry weight. The capability of dry matter production was higher for rice of the first crop season. Culms of the first crop rice contained 1.5-5.5 times more TNC than those of the second crop rice at heading, a result of higher TNC concentration and dry weight per hill. The production of TNC during grain-filling was supperior for the first crop rice. Regardless of crop season or location, the harvest TNC index (HTNCI) ranged between 0.93 to 0.98. In other words, the efficiency of utilizing TNC by the rice was extremely high. The contribution of preheading storage to yield were 17.8-22.5% and 11.6-17.9% for the first and second crops, respectively. No consistent relationship between N concentration in leaf blade at heading and final grain yield was observed. However, compared to the second crop, the first crop rice in Pingtung had lower leaf blade N but significantly higher yield, indicating the correlation between these two characters was not simple. Harvest N index (HNI) was 0.70-0.81 for the first and 0.65-0.76 for the second crop. The interaction between the translocation of N and TNC from vegetative tissue to the grain was suggested. Analysis of yield componts showed similar 1,000-grain weight and product of spikelet number per panicle by the percentage of ripened grain. The lower yield of the second crop rice was caused by few panicle number and lower contents of dry matter and TNC at heading. The enhancement of photosynthetic capability during grain-filling was also of utmost importance in terms of increasing the yield of second rice crops in Taiwan