Effects of ultraviolet radiation on three types of protective enzymes in Therioaphis trifolii

To clarify the effect of ultraviolet radiation (UV-B) on the activity of three protective enzymes (SOD, POD, and CAT) in Therioaphis trifolii, nymphs were exposed to 40 W UV-B radiation for 20, 30, 40, 50, and 60 min within 12 h of hatching. The nymphs were irradiated once a day continuously for 6 days and the activity of the protective enzymes was measured in the last 8 generations subjected to continuous exposure. The study showed that the activity of CAT and SOD first increased and then decreased with the extension of radiation time and the activity in all treated aphids was significantly higher than in the control (P < 0.05) in the same generation, and the maximum activity was 12.84 and 8.05 times that of the control, respectively. In each generation at 40 min of exposure, CAT activity was the highest, POD activity was the highest except in the F₅ generation, and SOD activity was the highest except in the F₆ generation. Secondly, the activity of CAT, SOD, and POD under the same treatment first increased and then decreased with each successive irradiated generation and the maximum activity was 12.84, 8.05, and 2.09 times that of the control, respectively. The activity of CAT and POD was the highest in the F₆ generation, except at 30 min, and SOD activity was the highest in the F₆ generation. These results showed that UV-B can significantly improve the activity of the protective enzymes (P < 0.05) in Therioaphis trifolii and that CAT and SOD play a key role under UV-B radiation.