| Summary: | 碩士 === 中興大學 === 農藝學系所 === 99 === In order to screen drought-sensitive and -tolerant rice mutants, rice growth responses to drought at different development stages were studied. Experimental results showed that rice growth was inhibited with decreasing water potential, and the coleoptile elongation had higher sensitivity to and proportionally inhibited by water stress, which was similar to the response of injury index of rice seedlings. After serial screening of drought-S and -T mutants, which were mutated from Indica-type rice var. IR64 by sodium azide, it seemed that more T-mutants were observed from 5 mM sodium azide mutation. However, drought tolerance trait is still variable in M3 and M4 generations. Due to the significant difference of drought-tolerance between Indica- and Japonica-type rice plants, based on the coleoptile elongation inhibition and injury index of seedlings, the role of osmoregulation through proline accumulation in roots played in drought tolerance was explored. Both an increased activity of Δ1-pyrroline-5-carboxylate synthetase (P5CS) and a decreased activity of proline dehydrogenase (PDH) in tolerant Indica-type IR64, confirmed the osmoregulation. In addition, that proline accumulation in roots thought ABA mediation under water stress was also proven by the exogenous application of ABA.
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