분리된 밀 잎에서 Paraquat에 의해 유도된 항산화 효소활성도의 변화

The present study was aimed to investigate the time- and concentration-dependent paraquat (PQ) effects in leaf segyrents of 7-day-old wheat seedlings on the degree of PQ-induced oxidative damages and developments of some major H₂O₂-scavenging enzymes such as catalase (CAT), guaiacol peroxidase (GPX) and ascorbate peroxidase (APX). In leaf segments incubated for 12 h under continuous light with different concentrations of PQ, PQ treatments did not have any apparent effects on the chlorophyll and carotenoid contents except for soluble proteins compared to the D.W. control. The level of MDA (malondialdehyde, a product of lipid peroxidation) was increased by little and little up to 0.25 μM PQ concentration, whereas it decreased rapidly at more than 0.5 μM PQ. In the development of activities of H₂O₂-scavenging enzymes, GPX activities did not show any changes compared to the DW. control under 0.25 μM PQ, while CAT and APX activities enhanced little by little up to 0.25 μM PQ. However, all enzymes activities inactivated remarkably at more than 0.5 μM PQ. At leaf segments after 24 h light incubation with PQ, PQ treatments at more than 0.5 μM concentration caused severe reduction of chlorophyll, carotenoid and soluble protein contents while there were no significant decreases under 0.25 μM PQ. The MDA levels also decreased rapidly at more than 0.5 μM PQ, however there was a progressive increment under 0.25 μM PQ. In the case of fWz-scavenging enzymes, the CAT and APX activities enhanced up to 0.25 μM PQ concentration and then reduced largely thereafter, although there was no significant difference in CAT activities between 12 h and 24 h incubations. In addition, GPX and APX activities in leaf segments for 24 h incubation were higher than those of 12 h incubation leaf segments under 0.25 μM PQ. On the above results, we suggested that the CAT and APX enzymes could be preferentially involved in protection against PQ-induced damages by PQ concentration-dependent manner in wheat leaf segment.