水稻幼苗叶绿体保护系统对干旱的反应

干旱条件下水稻耐旱品种湘中籼２号比不耐旱品种湘早籼１２号具有较低的质膜相对透性、叶绿素含量降低较少，表明耐旱品种受伤害较轻，两个品种的抗坏血酸。过氧化物酶（ＡｓＡ－ＰＯＤ）均降低，但耐旱品种降低较少。耐旱品种的谷胱甘肽还原酶（ＧＲ）活性在干旱初期提高，不耐旱品种的则变化不大。０．０１ｍｍｏｌ／Ｌ的百草枯和０．１ｍｍｏｌ／Ｌ的Ｈ２Ｏ２亦能诱导耐旱品种的ＧＲ活性，但对不耐旱品种的ＧＲ活性不受影响，说明可能是干旱诱导的氧化胁迫诱导了ＧＲ活性。干旱条件下两品种的抗坏血酸（ＡｓＡ）和还原型谷胱甘肽（ＧＳＨ）含量均是先升后降，但耐旱品种提高幅度较大。结果表明，耐旱品种的叶绿体保护系统的活性比不耐旱品种的高。

RESPONSES OF PROTECTION SYSTEM IN CHLOROPLASTOF RICE SEEDLINGS TO THE DROUGHT

Under drought condition, the drought-tolerant riee cultivar "Xiangzhongxian No.2" showed lower relative plasmalemma permeability and less reduction in chlorophyllcontent as compared with drought-sensitive cultivar "Xiangzaoxian No. 12" , whichindicated that the drought-tolerant cultivar was less demaged by drought stress. Ascorbate-peroxidase (AsA-POD) activity decreased in both cultivars, but less decreased in drought-tolerant one. The glutathione reductase (GR) activity increased at the beginning of droughtin drought-tolerant cultivar, but that did not change obviously in drought-sensitive one.The results also showed that GR activity could be induced by paraquat (0.01 mmol/L) andH2O2 (0.1 mmol/L) in drought-tolerant cultivar, but they had no effects on drought-sensitiveone, which indicated that the increase of GR activity in drought-tolerant cultivar underdrought stress might result from the induction by oxidative stress. In addition, the contentsof ascorbate (AsA) and reduced glutathione (GSH) showed a tendency of being increased atfirst, then decreased in both cultivars, but with greater increase in the drought-tolerantcultivar. The results suggested that drought-tolerant cultivar had better protectionsystem in chloroplasts against drought stress than the drought-sensitive cultivar.