中文摘要：

研究干旱胁迫下一氧化氮（Nitric oxide,NO）对水稻叶片光合速率、相对含水量及抗氧化系统的影响,旨在揭示 NO增强水稻耐旱性的作用机制。以常规粳稻日本晴为材料,在土培条件下于水稻分蘖盛期叶面喷施硝普钠（SNP,NO 缓释剂）和/或 cPTIO（NO 清除剂）后进行干旱处理,6 d 后,取样并分析叶片各生理指标。结果表明,与清水对照相比,干旱胁迫下,喷施100μmol/L SNP 可显著增强水稻耐旱性,叶片表现出较高的相对含水量和光合速率,较低的丙二醛和过氧化氢含量。相反,100μmol/L cPTIO 处理的水稻叶片光合速率明显低于对照,相对含水量略低于对照,而丙二醛和过氧化氢含量显著高于清水对照。进一步研究表明,干旱胁迫下喷施外源 SNP 的叶片具有较高的超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性,较低的抗坏血酸（AsA）含量和总谷胱甘肽（GSH＋GSSH）含量。此外,外源喷施 SNP 对水稻叶片过氧化物酶（POD）和抗坏血酸过氧化物酶（APX）活性影响不大,各处理间差异不显著。总之,以100μmol/L SNP 作为 NO 缓释剂处理的水稻干旱损伤较轻,干旱胁迫下叶片具有较高的 SOD 及 CAT 活性,这可能是 NO 增强水稻耐旱性的主要原因。

英文摘要：

To reveal the mechanisms that nitric oxide （NO）enhances drought tolerance in rice,we studied the effects of NO on leaf photosynthetic rate,relative water content and antioxidant system of rice under drought stress.After foliar spray of 100 μmol/L sodium nitroprusside （SNP,a NO donor）and/or 100 μmol/L cPTIO （a NO scavengers）, japonica nipponbare （Oryza sativa L）was subjected to drought stress during tillering stage in a plastic tank.Rice leaves were sampled for further physiological analysis at the sixth day after treatment.Results showed that foliar spray of 100 μmol/L SNP enhanced rice tolerance to drought stress,which showed higher photosynthetic rate and relative water content,but lower malonaldehyde （MDA）and hydrogen peroxide （H 2 O 2 ）contents in leaves when compared with the control,foliar spraying with deionized water.By contrast,the cPTIO treatment significantly reduced leaf photosynthetic rate and relative water content,and significantly increased leaf MDA and H 2 O 2 contents.Further study indicated that foliar application of SNP significantly increased superoxide dismutase （SOD） and catalase （CAT） activities,but observably suppressed ascorbic acid （AsA）content and total glutathione （GSH＋GSSH）contents under drought stress.However,it had no significant influence on peroxidase （POD）activity,ascorbate peroxidase （APX） activity and there were no significant difference among the four treatments.It was concluded that nitric oxide might increase the activity of SOD and CAT,resulting in improved drought tolerance in rice.