水稻為我國最重要的栽培作物，產量和品質為水稻栽培的兩大目標。澱粉是水稻榖粒的主要成分，穀粒內澱粉合成相關酵素活性表現，與水稻穀粒發育的量與品質有關，尤其與影響米質重要因子之直鏈性澱粉合成關係更為密切。台農67號是台灣普遍栽培的一個水稻品種，為台灣之高產代表品種之一，米粒的直鏈性澱粉含量約為20﹪，但米質及二期作產量仍有改進空間。SA419為疊氮化鈉誘變台農67號的突變體，其米粒直鏈性澱粉含量為8﹪，米質不同於台農67號，本研究以該突變體與台農67號為材料，調查其農藝性狀資料，及穀粒澱粉相關酵素表現與穀粒乾重累積和品質關係之探討。
結果發現水稻穗內不同部位穎花的產量貢獻程度有差異，SA419穗內不同部位穎花的產量貢獻程度卻相同，且SA419成熟穀粒的單粒粒重分布較台農67號集中，均為其優良特性。SA419一株穗數較少，一期作產量無法超越台農67號。二期作一株穗數與台農67號差距縮小，產量即高於高產的台農67號。一株穗數較少之因素，可藉由栽培方法改進。水稻充實期SUS、Invertase、Hexokinase、AGPase、UGPase、SSS和SBE等酵素的活性表現，與澱粉的累積有關，且SA419的穀粒充實較快速和較重的粒重，乃因比台農67號有較高活性之故。SA419的穀粒含較低量的直鏈性澱粉，可能因比台農67號有較低的GBSS和SDBE活性之故。穀粒著生位置會影響穀粒生長，因品種不同而改變。以台農67號而言，轉換蔗糖為澱粉的相關酵素活性降低，尤其穀粒充實早期更加明顯，與下位二次枝梗穀粒澱粉累積比上位一次枝梗穀粒低有關連。台農67號下位二次枝梗穀粒直鏈性澱粉含量較低可能因GBSS活性較低之故，此一現象在穀粒充實早和中期尤其明顯。由於上位一次枝梗穀粒和下位二次枝梗穀粒的GBSS活性無明顯差異，SA419的澱粉和直鏈性澱粉含量在兩部位間則無明顯差異。經由NBT酵素活性原位染色，發現水稻穀粒澱粉合成相關酵素主要在胚乳細胞表現，在穀粒發育初期所有胚乳細胞均有酵素活性；隨穀粒發育，酵素活性則由中心細胞往外層細胞失去活性；穀粒發育愈快，往外層細胞失去活性的速度愈快，NBT酵素活性的原位染色結果可提供一般生化分析的參考。希望本研究結果能應用於水稻研究，作為探討及改進台灣水稻產量及品質之參考。Rice is the most important crop in Taiwan. Yield and quality are the main goal for rice cultivation. Starch is the major constitutes in rice grains, therefore, the enzyme activities engaged in starch accumulation are closely related to the rice grain dry matter accumulation and grain quality, especially to amylose accumulation. The cultivar Tainung 67, one of high yield cultivar, is widely distributed in Taiwan, but the grain quality and the yield of second crop season are always needed to be improved. Recently a mutant SA419, mutated by sodium azide from Tainung 67 which contained 20% amylose content in rice grains, was isolated. The mutant SA419 with lower amylose content(8%)in grains has different grain quality in comparison with Tainung 67. In the present study, We compared rice cultivar Tainung 67 and mutant SA419 in the agronomic characteristics, and the relationship between grain dry mater accumulation or grain quality and sugar-starch conversion enzyme activities.
The results indicated that the grains located on different branches of panicle contributed different yield, but had the same contribution in mutant SA419. The mutant SA419 also had more concentration distribution of grain weight than cultivar Tainung 67. The mutant SA419, with less panicle number in the first crop, produced less yields than cultivar Tainung 67, but produced higher yield in the second crop season, the panicle number difference between two varieties decreased. The factor of growing less panicle number could be improved by cultural changes. The changes in the rate of starch accumulation correlated well with the changes in the activities of sucrose synthase, invertase. hexokinase, AGPglucose pyrophosphorylase, UDPglucose pyrophosphorylase, phosphoglucoisomerase, phosphoglucomutase, soluble starch synthase, granule-bound starch synthase, starch branching enzyme and starch debranching enzyme, during the grain filling period. The rapid grain-fill and shorter period of grain filling in mutant SA419, as compared with Tainung 67, were associated with its higher activity of starch synthesizing at the early phase of grain growth. The lower amylose content of SA419 grains (8%) in comparison with Tainung 67 grains (20%) was due possibly to their inferiority to synthesize amylose through granule bound starch synthase and starch debranching enzyme. The tested Tainung 67 and SA419 showed different starch and amylose accumulation patterns in different grain positions. In cultivar Tainung 67, the reduced activities of grain enzymes involved in starch biosynthesis, particularly during the early phase of grain filling, were related to the decreased starch accumulation for the grains located on proximal secondary branches as compared to the grains located on distal primary branches. The decreased amylose content in the grains of Tainung 67 located on proximal secondary branches was attributable to their lower granule bound starch synthase and starch debranching enzyme activities at early and mid phases of grain filling. In mutant SA419, significant changes were not observed in the activities of grain enzymes involved in sucrose to starch conversion between the grains located on distal primary and proximal secondary branches of panicle. As a result, little position effects were found in the contents of starch and amylose for these developing grains located on different branches. We found that the technology of enzymes activity in situ staining by NBT would apply to the enzyme involved to the rice grain sugar-starch conversion. The NBT in situ staining results showed that the enzyme activities expressed mainly on the endosperm. NBT staining was expressed at all the endosperm cell at the early phase of grain growth, and gradually reduced from central part of endosperm as grains growing, the faster grains growing, the faster reduction. The results of in situ enzyme activity staining could offer some suggestions on the biochemical analysis for physiological investigation.圖目錄 II
表目錄 VI
縮寫字對照表 VII
中文摘要 1
第一章 緒言 3
第二章 前人研究 5
第三章 水稻台農67號與SA419產量及產量構成要素之
差異性研究
2-1 前人研究 13
2-2 材料與方法 14
2-3 結果 16
2-4 討論 18
第四章 穀粒充實期澱粉合成之研究
2-1 前人研究 31
2-2 材料與方法 32
2-3 結果 37
2-4 討論 39
第五章 水稻穀粒澱粉合成酵素之原位（in situ）染色
2-1 前人研究 48
2-2 材料與方法 49
2-3 結果 51
2-4 討論 53
第六章 水稻穀粒著生位置與澱粉合成之關係
2-1 前人研究 65
2-2 材料與方法 66
2-3 結果 67
2-4 討論 70
第七章 綜合討論與結論 78
英文摘要 86
參考文獻 8
