桑叶缺铁性失绿症与超氧化物歧化酶活性及膜脂过氧化的关系

RELATION BETWEEN CHLOROSIS DUE TO IRON DEFICIENCY AND ACTIVITY OF SUPEROXIDE DISMUTASE AND MEMBRANE LIPID PEROXIDATION IN MULBERRY LEAVES

研究了生长在石灰性土壤上的桑树春季新梢不同叶位叶的超氧化物歧化酶(SOD)、过氧化物酶(POX)、过氧化氢酶(CAT)的活性及膜脂过氧化产物丙二醛(MDA)的含量和电导率的变化。发现:(1)失绿叶的膜脂过氧化产物MDA的含量明显高于正常叶,含量增加的百分率上位叶大于中位叶和下位叶。(2)细胞膜透性(电导率表示)与膜脂过氧化水平的增加及变化趋势相平行。(3)失绿叶的SOD、POX及CAT的活性有不同程度的下降,SOD活性下降较小,而POX、CAT的活性下降幅度较大。(4)膜脂过氧化水平、膜透性的增加和SOD、POX、CAT活性的降低与叶绿素含量的下降变化相一致。说明在桑树缺铁性失绿过程中,可能存在着活性氧毒害而损伤细胞膜的结构,破坏生理代谢的协调性,加速衰老。

The changes of membrane permeability (conductivity) ,malondialdehyde(MDA)con-tent (the product of membrane lipid peroxidation) ,the activities of superoxide dismutase (SOD) ,peroxidase(POX)and catalase(CAT)in spring shootlet leaves of different positions of mulberry growing in limysoil have been studied. They were found that(l)MDA content in chlorotic leaves was obviously higher than that in normal leaves,and the percentage of the increased content in upper leaves of shoot was larger than those in middle and lower leaves of shoot. (2) The increase and changing tendency of membrane permeability were parallel with those of membrane lipid peroxidation. (3) The activities of SOD,POX and CAT in chlorotic leaves decreased in varying degrees. The decrement of SOD was slight while those of POX and CAT were marked. (4)The increase of membrane lipid peroxidation, membrane permeability and the decrease of the activities of SOD,POX and CAT coincided with the decline of chlorophyll content. These results indicate that oxigen-free-radicals poison may exist to destroy the structure of cell membrane and the consistency of physiology metabolism and to speed up the ageing of the leaves in the process of chlorosis due to iron deficiency in mulberry trees.