一、二期作水稻充實期之老化與轉流的差異性比較研究

Abstract

本試驗選擇二水稻品種，分別於一、二期作培植於田間，在穀粒充實期間，分析分蘗各部位之器官乾重、蛋白質、以及非構造性碳水化合物之變化，以比較期作問物質之轉移與配間之情形，並分析葉片內水溶性蛋白質、蛋白質分解酵素、游離膠基酸及α-澱粉分解酵素，以比較期作間植株老化之程度。 試驗結果顯示，在穀粒充實期，二期作水稻合成乾物質與非構造性碳水化合物之能力較一期作為高。在開花時，營養器官貯存之非構造性碳水化合物，一期作高於二期作，但收穫時，二期作高於一期作。非構造性碳水化合物之轉移百分比，一期作平均約為20%，二期作平均為8%。由於二期作具有較高之同化能力，故仰賴開花前貯存性物質之比例較低，且收穫時，殘留於營養器官內之非構造性碳水化合物也較多。此顯示，積儲容積是限制水稻產量之主要因素。二期作穀粒充實期間，氣象條件適宜，導致本試驗二期作產量優於一期作。穀粒充實時，期作間蛋白質累積於穗部之量相似，但二期作殘留於營養器官之蛋白質較多，有利於植株代謝之平衡。劍葉中水溶性蛋白質含量較高，蛋白質分解酵素活性維持恆定α-澱粉分解酵素活性較高，老化之現象也較其他葉片為緩。這些資料，充分顯示穀粒充實期間，劍葉是主要之同化代謝器官。 不過，本試驗之結果顯示，期作對於水稻植株葉片老化程度之影響不顯著。控制葉片老化程度之因子，可能是植株內始源與積儲之間營養需求與供輸，尤其是蛋白質之供輸間之關係。 The effect of cropping seasons on the dry matter accumulation and the leaf senescence pattern of two field-grown rice (Oryza sativa L.) genotypes were investigated throughout the ripening period. The translocation of protein and nonstructural carbohy-drate, protease and aipha-amylase activities, free amino acids and soluble sugars were determined in various leaves. The relation between the senescence pattern of leaves tissue and cropping seasons was also evaluated. The results indicated that the total dry matter productivity in second cropping season was higher than that in first cropping season. This was attributed to the higher solar radiation and moderate air temperature in 1981 growing year. The contribution of pre-anthesis carbohydrate to final yield was 20% and 8% for first and second cropping sassons, respectively. The data also indicated that the nonstructural carbohydrate remaining in vegetative residue of second crop was higher than that of first crop, suggesting that the sink capacity was the major factor limiting rice yield. The partitioning of protein within rice tiller followed a pattern similar to that of the nonstructural carbohydrate. The higher protein content in leave tissue of second rice crops might delay the leaf senescence to some degree and thus, maintain higher assmilatory activities during ripening. Based on the results of this study, it was concluded that the major factor regulating the leaf senescence might be resided in the nutritional compound demand and supply (e. g., protein), between source and sink of rice plant.