Physiological characterizations of salt tolerance at germaination and seedling stages in rice (Oryza sativa L.) Tainung 67 mutants

• Main Authors: Woei-Shyuan Jwo, 卓緯玄
• Other Authors: Hungchen E. Yen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/04134491658148755366

碩士 === 國立中興大學 === 生命科學院碩士在職專班 === 95 === Rice (Oryza sativa L. ), one of the most important cereal crops in the world. There are three major cereal crops in the world, namely rice, wheat, and maize and totally offer 50% of the calorie sources to the world population. Soil salinity is a complex and harmful threat faced by plants. High concertrations of salts will suppress crops growth and interfer physiological metabolisms. Rice is a salt-sensitive crop and the soil salinity decreases the yield. This thesis is aimed at the characterizations of physiological responses to salt stress in rice. Mutants of Tainung 67 ( TNG 67 ) rice variety were screened for salt tolerance at seedling stage. Two mutant strains were successfully identified with ST-099, a salt-tolerant strain, and ST-300, a salt-sensitive strain. Their agricultural characteristics showed no difference in growth. The tolerance to salt of ST-099 (salt-tolerant strain) was the same at germination stage and seedling stage. ST-099 has higher relative water content (RWC) and relative growth rate (RGR) than salt-sensitive strain ST-300 under salt stress. On the other hand, ST-099 is more sensitive to water-deficit stress at seedling stage than at germination stage. The results suggest that the adaptation mechanisms to salt and water-deficit stress are not identical. Elemental Analyses showed salt-sensitive strain ST-300 had a lower potassium content, a higher sodium content, a higher chlorine content, and a higher Na+/K+ ratio. There was no significant difference in the amount of calcium at initial stage of salt stress suggesting that delay of Ca2+-mediated signaling was a factor contributing to its salt sensitivity. As for salt-tolerant ST-099 strain, it had the lowest sodium content and Na+/K+ ratio. A rapid increase in calcium concentration at initial stage of salt stress was very prominent in this salt-tolerant strain. Furthermore, other evidences leaded us to hypothesize that this strain might be able to use excess Na+ for osmoregulation, and as the result, the rate of decrease in relative water content was much slower in ST-099. Under the same NaCl concentration, the salt-sensitive strain had a higher proline concent, and the salt-tolerant strain accumulated much lower level of proline suggesting proline accumulation is a result of injury caused by salt stress.