秈稻與稉稻係起源於不同地區,對水分的需求亦不同,本試驗以秈稻IR64和稉稻TNG67為材料進行耐旱性差異之研究,根據此兩型水稻的胚芽鞘伸長及幼苗傷害指數調查結果,顯示IR64較TNG67耐旱。進一步分析脯氨酸含量變化,發現於PEG處理控制-0.2 MPa水份潛勢3天後IR64根部顯著累積脯氨酸,其合成酵素"P5CS"也於PEG處理後逐漸增加,同時降解酵素PDH的活性則逐漸降低;相反地,TNG67於PEG處理後脯氨酸含量無明顯增加,P5CS活性亦無提升,且PDH卻不減反增。此外,外施植物荷爾蒙ABA可誘導脯氨酸累積,與PEG處理的結果相似。因此推論,乾旱下係經由ABA誘導脯氨酸累積,以助提升水稻之耐旱性。
The mechanism of drought tolerance in rice was studied using an Indica-type IR64 and a Japonica-type TNG67 varieties. An increase of Δ1-pyrroline-5-carboxylate synthetase (P5CS) activity and a decrease of proline dehydrogenase activity as well as an accumulation of proline were observed in tolerant IR64 rice under drought stress. The effects of both exogenously applied abscisic acid (ABA) and an inhibitor of ABA biosynthesis confirmed the role of proline-mediated osmoregulation via an induction of P5CS activity controlled by the plant hormone ABA in the drought tolerance of this staple crop.