缺锌胁迫对水稻叶绿体抗氧化系统的影响

采用营养液培养方式,设置0,1.0×10^-10和1.0×10^-6mol/L 3个锌处理水平,研究了缺锌胁迫对水稻叶绿体活性氧水平、膜脂过氧化、抗氧化剂含量及抗坏血酸（As A）-谷胱甘肽（GSH）循环系统中相关酶活性的影响.结果表明：1.0×10^-10mol/L锌处理下,水稻叶绿体中H2O2,O2.^-和丙二醛（MDA）的含量显著升高,表明缺锌造成了水稻叶绿体内的氧化胁迫;抗坏血酸含量在1.0×10^-10mol/L锌水平上达到最高,而谷胱甘肽含量随缺锌程度的增加呈递减趋势;超氧化物歧化酶、抗坏血酸过氧化物酶、谷胱甘肽还原酶及单脱氢抗坏血酸还原酶等As A-GSH循环中的关键酶活性均于潜在缺锌（1.0×10^-10mol/L锌）下达到最大值,而在严重缺锌（0 mol/L锌）下又显著下降.研究表明：一定程度上缺锌可诱导水稻叶绿体内As A-GSH循环系统中的抗氧化剂水平和抗氧化酶活性增加,以减少活性氧的产生与膜脂过氧化的作用;但严重缺锌条件下水稻叶绿体中氧化胁迫突破了抗氧化保护系统的保护能力,使水稻受到伤害.

Effects of zinc deficiency on antioxidant system in chloroplast of rice

The rice plants were hydroponically treated with 1. 0 × 10^-6（ control）,1. 0 × 10^-10（ potential Zn deficiency） and 0 mol / L Zn（ severe Zn deficiency）. The effects of Zn deficiency on reactive oxygen species,membrane lipid peroxidation,antioxidant contents,and the activities of enzymes in the ascorbic acid（ As A）-glutathione（ GSH） cycle system in the isolated chloroplast were comprehensively investigated. The results showed that contents of H2O2,O2.^- and MDA in chloroplasts were significantly increased in response to Zn deficiency,implied the severity of oxidant stress. The ascorbic acid content was increased with treatments of potential Zn deficiency but markedly decreased when subjected to severe Zn deficiency. Conversely,the contents of glutathione,another important antioxidant in GSH-GSSH cycle,showed a decreasing trend paralleled to the increasing severity of zinc deficiency. The activities of main enzymes in As A-GSH cycle,including superoxide dismutase（ SOD）,ascorbate peroxidase（ APX）,glutathione reductase（ GR） and monodehydroascorbate reductase（ MDHAR）,were increased by potential Zn deficiency（ 1. 0 × 10^-10 mol / L）,but decreased significantly under severe Zn deficiency（ 0 mol / L）. The results suggested that a certain extent of Zn deficiencystimulated the capacity of antioxidant systems in chloroplast to reduce reactive oxygen species levels and alleviate the peroxidation of membrane lipid,whereas critical Zn deficiency broke down the antioxidant systems in chloroplast,resulting in severe oxidant damage of rice plants.