大豆於鹽逆境下glutathione reductase於其耐鹽性機制之生理功能

Role of Glutathione Reductase and Related of Enzymes in Salt-tolerant Mechanism of Soya bean Plants Grown under Salt-stress Condition

大豆生長於鹽逆境情況下，若經馴化，其葉細胞中的glutatione reductase等酵素活性，均比未馴化植物高的很多。這些酵素於正常生長情況下均分佈於葉綠體，但在鹽逆境下，其活性大多發現於細胞質中。由於這些酵素活性的增加，使細胞中由於鹽逆境所產生的過氧化氫濃度減少，以致減少細胞膜的脂質過氧化作用，而保持細胞膜的完整性。由於細胞膜未被過氧化氫所破壞，所以細胞中的離子或其它物質，則不會滲露出來，也因而使細胞能夠保持適中的滲透壓，以使植物於鹽逆境情況下不致脫水而不能生存。另外，glutathione reductase活性也使細胞中的GSH/GSSG含量比例增加。此比例的提高，也可使植物細胞中含有－SH的酵素保持其還原性而不被氧化而失去其催化活性。所以高濃度的GSG/GSSG比例，對植物的耐鹽性也有極重要的生理功能。

Salt-acclimated soybean plants had higher activities of glutathione reductase and of its related enzymes, ascorbate peroxidase, and dehydroascorbate reductase, than those of non-acclimated plants grown under the salt-stress condition. Those enzymes, which mainly distributed in different organelles under normal growth condition, became predominantly in cytosol under this adverse environment. Those H2O2 scavenging enzymes might protect the plasma membrane of leaf cells from lipid peroxidation. The maintaining of integrity of plasma membrane of leaf cells by reduction of the lipid peroxidation might reduce the level of ionic leakage out of cells, and so favors plants to adapt the salt-stress environment. Besides, the glutathione reductase also kept high ratio of GSH/GSSG in cytosol. The high ratio of GSH/GSSG may have positive effects on plants to tolerate the salt-stress environment.