缺镁对龙眼叶组织活性氧代谢及膜系统的影响

通过水培试验，研究缺镁对龙眼幼苗叶组织活性氧代谢及膜脂过氧化作用的影响。结果表明，随着缺镁症状加重，龙眼叶片细胞内Ｋ＋外渗量，ＭＤＡ含量、Ｏ２净产生速率和Ｈ２Ｏ２含量增加，活性氧清除系统的酶（ＳＯＤ、ＡＳＡ—ＰＯＤ、ＧＲ）活性提高。抗氧化物质（ＡｓＡ、ＧＳＨ）含量先升高，后下降。缺镁龙眼叶片抗氧化物含量和活性氧清除酶活性的提高是龙眼抵御活性氧伤害的一种适应性反应。缺镁龙眼活性氧伤害的原因可能与龙眼ＣＯ２同化能力下降，光合产物运转受阻有关。 

Effects of Magnesium Deficiency on Active Oxygen Metabolism and Membrane System of Longan(Dimocarpus longana. Lour)Leaves

The effects of magnesium deficiency on active oxygen metabolism and membrane lipid peroxidation in leaves of longan (Dimocarpus Longana. Lour) young seedlings were studied through hydroponic experiment In Mg-deficient leaves, the exudation of K',the contents of malondialdehyde (MDA) and H2O2 as well as the net rate of 02.' generation increased progressively with the severity of leaf chlorosis,. Under Mg deficiency stress,the activities of superoxide dismutase and H2O2 scavenging enzymes (ascorbate peroxidase,glutathione reductase) increased, the concentrations of antioxidants (ascorbate, reduced glutathione) increased at first and then decreased. Elevated levels of antioxidants,superoxide dismutase and H2O2 scavenging enzymes in Mg-deficient leaves can be interpreted as an adaptive response to active oxygen stress, which caused membrane lipid peroxidation and plasma membrane damage. It is suggested that in Mg-deficient leaves, the restriction of photoreductant utilization in CO2 fixation and photosynthate exportation led to a higher potential for photogeneration of toxic O2 species.