渗透胁迫下稻苗中铁催化的膜脂过氧化作用

Iron-Catalysed Lipid Peroxidation in Rice Seedlings Under Osmotic Stress

在－０．７ＭＰａ渗透胁迫下，水稻幼苗体内和Ｈ２Ｏ２大量产生，Ｆｅ２＋积累，膜脂过氧化作用加剧。水稻幼苗体内Ｆｅ２＋含量与膜脂过氧化产物ＭＤＡ含量呈极显著的正相关。外源Ｆｅ２＋、Ｆｅ３＋、Ｈ２Ｏ２、Ｆｅ２＋＋Ｈ２Ｏ２、ＤＤＴＣ均能刺激膜脂过氧化作用，而铁离子的螯合剂ＤＴＰＡ则有缓解作用。ＯＨ的清除剂苯甲酸钠和甘露醇能明显地抑制渗透胁迫下Ｆｅ２＋催化的膜脂过氧化作用。这都表明渗透胁迫下水稻幼苗体内铁诱导的膜脂过氧化作用主要是由于其催化Ｆｅｎｔｏｎ型Ｈａｂｅｒ－Ｗｅｉｓｓ反应形成ＯＨ所致。

Seedlings of hybrid rice (Oryza sativa L. )were exposed to osmotic stress by PEG 6000 (- 0. 7 MPa) and the contents of ferrous iron (Fe2+ ), hydrogen peroxide (H2O2) and malondialdehyde (MDA) and the rate of production of superoxide radical ( ) were measured. Under osmotic stress, the increases of contents of Fe2+ and H2O2and rate of O2 producction were accompanied by an increase of content of MDA(Fig. 1 ). A very correlation (P < 0. 01 ) was observed between Fe2+content and MDA content (Fig. 2 ).Pretreatment with Fe2+, Fe3+, H2O2,Fe2++ H2O2 and the inhibitor of SOD, sodium diethyldithiocarbamate (DDTC ), obviously promoted lipid peroxidation, but the iron chelator, diethylenetriaminepentuacetic acid (DTPA ), retarded the increase of MDA (Fig. 3, 5 ). Application of the hydroxyl radical scavengers, mannitol and sodium benzoate, markedly inhibited the lipid peroxidation of Fe2+ mediated under osmotic stress (Fig. 6 ). These results indicate that iron-stimulated lipid peroxidation in rice seedlings is mainly due to the formation of highly reactive hydroxyl radical (OH ) by superoxide driven Fenton reaction catalysed by iron under osmotic stress, but a complex between oxygen and different valence states of iron has little effect on lipid peroxidation.