| Summary: | 碩士 === 國立嘉義大學 === 農藝學系研究所 === 105 === This study aimed the effects of water stress (sorbitol, drought and PEG) on seed germination and seedling growth in foxtail millet. Also aimed to crosstalk of different varieties, carbohydrates, phytohormones and osmotic treatment on the modulation of shoot regeneration in millet callus. Ten of Taiwanese millet varieties were used. The results showed that the seed germination and earlier seedling growth have no significant different either containing sucrose or not. However, sucrose is benefit to promote shoot and root growth later. Besides, the seed germination and seedling growth of all millet varieties are decreasing accompanied by increase of sorbitol concentration in germination medium. TCS1 has the best growth parameters under different germination condition, TTS1 and TTS6 in opposite are the most sensitive to sorbitol response. In addition, we used chlorophyll fluorescence (Fv/Fm) decreased to 0.2 as the indicator to represent the drought tolerance ability at seedling stage under drought stress treatment. The results showed that TTS4 and TTS6 are the most tolerant cultivars when stop to irrigate for 11 days, but, TCS1 and TT7 have the highest survival rate recover from 24% PEG treatment. The inconsistence of drought tolerance ability among different screening system may cause from the uniformity for stress treatment. TTS1, TCS1, TT8, and TT9 were further selected to compare their response of callus induction and shoot regeneration under different percentage of sorbitol treatment. It showed that sorbitol is not only as the osmotic agent but also as the carbon source in millet. It also showed the callus fresh weight and dry weight of TCS1 and TT9 are significant higher than TTS1 and TT8 in callus induction medium containing sorbitol. The embyongenic competence, rooting rate, and green spot rate are decreased of TT8 when the kinetin concentration was increased to 5 ppm of MSK2N0.5 shoot regeneratin medium. However, the shoot regenerations frequency of TTS9 will increased at the same regeneration condition. In conclusion, further research is necessary to clarify the possible roles and metabolic pathway of sorbitol under drought tolerance and shoot regeneration process in millet callus.
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