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水稻葉片葉綠素生合成與降解途徑之研究
Study on the Chlorophyll Biosynthetic and Degradative Pathways in the Leaves of Paddy Rice
摘要
本研究旨在探討水稻品種農林8號及其不同程度缺乏無葉綠素b之突變種，於生育期間葉片之葉綠素（chlorophyll，Chl)、生合成中間物包括protoporphyrin IX （PPIX）、magnesium protoporphyrin IX（MGPP）及protochlorophyllide（Pchlide）與降解代謝物包括chlorophyllide（Chlide）、pheophytin（Phe）及pheophorbide（Pho）等含量變化與降解途徑，水稻肥培管理、遭遇病蟲害逆境及生育階段不同等因素都會影響色素的組成。研究結果顯示，水稻品種農林8號之Chl及其代謝物含量皆明顯高於突變種。Chl及Phe等極性較小之代謝物，其含量隨生育日數增加而下降，吡啉（PPIX、MGPP、Pchlide）及Chlide等極性較大之代謝物，其含量同樣亦隨生育日數增加而下降。水稻品種農林8號及其突變種在生育階段前期，也即營養生長期至生殖生長期，葉綠素之降解途徑傾向以Chl→Phe→Pho為主要降解途徑（major route），而以Chl→Chlide→Pho為次要途徑（minor route）；但隨著葉片逐漸成熟與老化，其葉綠素降解之途徑卻有明顯的不同，亦即在生育階段後期，也即生殖生長期至成熟期，葉綠素之降解途徑傾向以Chl→Chlide→Pho為主要降解途徑，而以Chl→Phe→Pho為次要途徑。藉由建立水稻生育期間色素生合成及降解途徑變化，並以此為基礎，探討色素含量與反射光譜之關聯性，未來將可利用非破壞性之方法輔助應用於判讀水稻生長狀態、生育時期、肥培管理、病蟲害預警及最終產量預估，以期達遙測技術在精準農業應用之實務化。
並列摘要
We examined the contents of chlorophyll (Chl), biosynthetic intermediates (protoporphyrin IX, PPIX; magnesium protoporphyrin IX, MGPP; protochlorophyllide, Pchlide), and degradative intermediates (chlorophyllide, Chlide; pheophytin, Phe; pheophorbide, Pho) in the leaves of rice with five different types of chlorophyll b-deficient or -lacking mutants during their growth and development. The levels of less polar (LP) intermediates such as Chl and Phe decreased with increasing growth stage, and the levels of more polar (MP) intermediates such as porphyrins (PPIX, MGPP, Pchlide), and Chlide were also decreased. The biosynthetic and degradative rate of Chl in rice variety Norin No. 8 was higher than that in tested rice mutants due to smaller amounts of Chl and intermediates. Chl→Phe→Pho was the major route of Chl degradation at vegetative stage in five rice lines, while Chl→Chlide→Pho was the minor route. When leaves were aging and senescent, Chl→Chlide→Pho was the major route, and Chl→Phe→Pho became the minor route of Chl degradation.