大豆種子與莢果壁非構造性碳水化合物與氮素含量之變化

Abstract

以大豆品種十石為材料，於1982及1983年夏作進行試驗，在生殖生長期間密集取樣，調查分析第 6-8 節位莢果壁與種子內乾物質、非構造性碳水化合物（TNC）及全氮（N）含量之變化，以明瞭大豆種子充實與TNC及N之利用情形。莢果壁內TNC濃度於R3-R4期最高，其後有下降趨向，但均維持於5-8%之間；N濃度則於 R4 期以後持續降低，顯示可充份轉移至種子。種子內TNC濃度於快速充實期間（R6）最高，而N素濃度之變化甚微，亦即種子乾物質與N素之累積有平行關係存在。莢果壁內TNC含量在R6期以前與種子TNC含量並行增加，在成熟期時僅小幅減少，對種子充實之重要性可能極為有限；莢果壁內所含N素在種子充實期問可大量轉移，亦即具有較高的利用效率，唯種子含N量由莢果壁轉移者，估計最高不超過9%。種子對莢果壁TNC與N素之利用程度有異，兩種營養要素亦可能經由不同途經轉移。 Soybeans (cultivar Shih-Shih) were grown in the summer crops of 1982 and 1983. Extensive samplings were made on the 6th to 8th nodes during pod-filling for the determination of dry weight and concentrations of TNC (total nonstructural carbohy-drates) and N in the pod wall and seeds. TNC concentrations in the pod wall peaked at R3-R4 stage and showed a very slight decreasing tendency afterwards. On the con-trary, N concentrations decreased continuously and markedly after R4 stage, indicating efficient translocation of N from pod wall to the seeds. Maximum TNC concentration in the seeds was observed at R6, or rapid grain-filling stage. However, N concentrations remained rather constantly during the whole grain-filling period. It is suggested that soybean seeds accumulated dry matter and N at a similar rate. Amount of TNC in the pod wall increased up to R6 stage and the decrease thereafter was minor. In other words, carbohydrates stored in pod wall was not quantitatively important to the devel-oping seeds. N could be translocated efficiently from pod wall to seeds after R5 stage. However, only 9% of total seed N was estimated to be provided by the pod wall. Extent of utilization of pod wall TNC and N by the soybean seeds varied, presumbly paths of translocation for the two nutrients were also different.