镉诱导油菜叶片氧化胁迫及硫化物的络合作用

Cadmium-induced peroxidation and production of sulfur-related complex in the leaf of oilseed rape

研究了不同浓度Cd 0、10、20、30、40μmol/L 对油菜 BrassicanapusL. 油研-8号 叶片H2O2积累、膜脂过氧化作用以及与硫代谢有关的抗镉机制.结果表明,随着Cd处理浓度的增加,叶片中H2O2及MDA的积累量均较对照显著增加,但对缺硫处理组 +Cd-S 与未缺硫处理组 +Cd+S 无显著差异.10～30μmol/LCd诱导过氧化氢酶 Catalase,CAT 、过氧化物酶 Guaiacolperoxidase,POD 的活力提高,40μmol/LCd对CAT活力有抑制作用.+Cd-S组的POD活力显著高于+Cd+S组.在Cd的诱导下,根部非蛋白巯基及酸不稳定性硫的含量大幅度增加.缺硫处理可明显阻碍上述含硫化合物的合成,从而加重Cd对叶片的伤害.上述结果表明,Cd对活性氧清除酶活性的诱导提高并非是抗镉关键途径,而与硫代谢有关的对Cd的络合作用才是油菜抗镉的重要机制.

Seedlings of oilseed rape (Brassica napus L.) 'Youyan No.8' were exposed to Cd at 0, 10, 20, 30 and 40 μmol/L concentration in 1/5 Hoagland nutrient solution supplied with and without sulphate for 7d. Treatments with Cd at 10~30 μmol/L induced a general increase in activities of guaiacol peroxidase (POD) and catalase (CAT) in leaves. However, the addition of 40 μmol/L Cd caused CAT activities to decrease. A greater promotion in activities of the enzymes with +Cd-S treatment than that with +Cd+S was observed. Cd also induced increases in H2O2 and lipid peroxidation levels, but no significant differences in H2O2 and TBArm levels between the +Cd+S and +Cd-S treatments were found. Compared with +Cd+S, +Cd-S treatment resulted in severe injury in leaves. Roots treated with +Cd+S showed a greater stimulation of nonprotein thiols and acidlabile sulfide production than those treated with +Cd-S. This observation suggested that under Cd stress oilseed rape depended on more thiol production to bind the heavy metal, while the increases in POD and CAT activities seemed to be of the least importance for the defense against Cdinduced oxidation stress.