渗透胁迫下水稻幼苗中叶绿素降解的活性氧损伤作用

ACTIVE OXYGEN DAMAGE EFFECT OF CHLOROPHYLL DEGRADATION IN RICE SEEDLINGS UNDER OSMOTIC STRESS

水稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）幼苗在渗透胁迫下，随着胁迫强度的增加及时间的延长，Ｃｈｌ降解加剧，活性氧Ｏ－·２ 、Ｈ２Ｏ２ 及脂质过氧化产物丙二醛（ＭＤＡ）含量明显增加，抗氧化剂抗坏血酸（ＡｓＡ）还原型谷胱甘肽（ＧＳＨ）及胡萝卜素（ＣＡＲ）含量显著降低，叶绿素蛋白复合体（Ｃｈｌ－Ｐｒｏ）结合度松弛． Ｃｈｌ含量的降低和Ｏ－·２ 、Ｈ２Ｏ２ 及ＭＤＡ 含量呈显著的负相关，与ＡｓＡ、ＧＳＨ及ＣＡＲ含量的下降呈良好的正相关性．ＡｓＡ、α－生育酚（ＶｉｔＥ）及甘露醇预处理可使胁迫诱导的ＭＤＡ 增多及Ｃｈｌ降解延缓，而Ｆｅ２＋ 、Ｈ２Ｏ２ 及Ｆｅｎｔｏｎ 反应则刺激ＭＤＡ 增加． Ｆｅｎｔｏｎ 反应可加速Ｃｈｌ降解． 渗透胁迫下水稻幼苗Ｃｈｌ的降解可能主要是由Ｏ－·２ 和Ｈ２Ｏ２

The changes of chlorophyll (Chl) content and contents of protochlorophyllide (Pchl), superoxide radical (O -· 2) and hydrogen peroxide (H 2O 2), malondialdehyde (MDA), ascorbic acid (AsA), glutathione (GSH), carotenoid (CAR) and the binding capacity of chlorophyll protein (Chl Pro) in rice (Oryza sativa L.) seedlings exposed to osmotic stress induced by PEG 6000 (-0 5 MPa, -0 8 MPa) were investigated to explore the relationship between Chl degradation and active oxygen effect.Under osmotic stress, Chl degradation was accompanied by the increase of contents of O -· 2,H 2O 2 and MDA and the decrease of contents of antioxidants AsA, GSH and CAR. The binding of Chl Pro was loosened with the change of time and intensity of osmotic stress. Pretreatment with scavengers for active oxygen, such as AsA, α tocopherol and mannitol retarded lipid peroxidation and reduced the oxidative injury of Chl, but Fe 2+ ,H 2O 2 and Fenton reaction promoted the formation of MDA. The Fenton reaction accelerated the degradation of Chl. The results indicate that Chl degradation in rice seedlings induced by osmotic stress may be mainly due to the formation of more active hydroxyl radicals ( ·OH) through Fenton reaction and Haber Weiss reaction.