2006-08-012024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/689981摘要：水稻為全世界一半人口之主要糧食作物，面臨人口增加及耕作面積減少的壓力，提高水稻單位面積產量則為重要的研究發展趨勢。水稻中澱粉含量為主要之產量指標，影響水稻穀粒中澱粉累積量的因子為醣供源組織 (source tissue)行光合作用，將二氧化碳固定於碳水化合物之能力；儲存組織 (sink tissue)累積澱粉的潛力及sink-source組織間醣類轉化和運送之效率。穀粒充實期所需之醣類主要來源有兩大類：(1)生殖生長期，葉部光合作用之產物，其做為一直接供應源；(2)於營養生長期預先儲存於莖部之碳水化合物。目前對於光合作用效率之提升以及穀粒中澱粉之合成機制已有較清楚之研究，但對於在莖部澱粉代謝之調控機制則仍不清楚。Ishikawa等人指出水稻之產量與抽穗前碳水化合物之累積量成正相關。水稻莖部組織 (含葉鞘及莖稈)為一暫時性儲存器官 (temporary sink tissue)，葉鞘在抽穗或開花前會快速大量累積澱粉，其為影響水稻產量之重要因子。如能增進葉鞘temporary sink tissue組織中澱粉累積量，並瞭解其後續如何由sink tissue轉化成source tissue.<br> Abstract: Rice (Oryza sative) is the staple food for half the world’s people. It will be a challenge to produce enough rice for the increasing population on decreasing agricultural area. Starch content is an important indicator for the yield of rice. Starch accumulation in grains was determined by the ability of CO2 fixed to carbohydrate through photosynthesis in source tissue (e.g. leaf), capacity of starch accumulation in sink tissue (e.g. grain), and efficiency of carbohydrate transportation between sink and source tissues. There are two major carbohydrate sources for grain filling: (1) assimilates originated from photosynthate that was transported to grains directly during the reproductive stage; (2) starch stored in stem during the vegetative stage role as another key carbohydrate source for grain filling. Stem of rice (included leaf sheath and culm) played a role as a temporary sink tissue. Starch was accumulated rapidly in leaf sheath before heading or anthesis, and then decreased during heading for providing the carbon source for grain filling. Ishikawa et al. indicated that there was a positive correlation between grain yield and carbohydrate accumulation in stem before heading. However, it is still unclear the regulations of starch synthesis in temporary sink tissue, leaf sheath. Since it is an important factor to determine the rice yield, increasing the starch accumulation in temporary sink tissue and understanding the mechanism of sink-source tissue transition of leaf sheath may help us to improve the rice production. Therefore, an effort will be made in this project to study the regulatory mechanism of starch metabolism in vegetative organs of rice. At first, the study will be focused on the expression and regulation of starch synthesis-related genes in leaf sheath during development stages, and the effect of environmental factors (e.g. temperature) on starch synthesis in this tissue. Studies on the correlation between starch accumulation and the expression of genes encoded enzymes involved starch synthetic pathway in leaf sheaths may illustrate which starch synthesis-related gene(s) is the major factor to control the starch content on the development stages, especially on the sink-source transition stage. Then, according to the cis-acting element analysis by promoter assay in transgenic rice to study the mechanism of starch temporarily stored in leaf sheath. Furthermore, microarray will be used to screen the genes that involved in the sink-source transition of leaf sheath. It will help us to understand the signal transduction and upstream regulatory pathway for rapid starch synthesis in leaf sheath before heading and sink-source transition of leaf sheath. This study will be useful to improve rice production in the future.澱粉水稻葉鞘暫時性儲存器官starchriceleaf sheathtemporary sink tissue