Influence of ionizing irradiation on the antioxidant enzymes of Vicia faba L.

Abstract

The seeds of Vicia faba L. Giza 834 were exposed to γ-irradiation at dose levels of 2.5, 5.0, 10.0 and 20.0 kGy and after that exposed to He-Ne (632.8 nm) or diode (650.0 nm) laser irradiation for 5 min. The activities of POD, APOX, CAT, SOD and GST enzymes were significantly stimulated and this stimulation reached its maximum at a dose level of 5.0 kGy for enzymes POD, APOX, CAT and SOD, but for GST enzyme at a dose level 10.0 kGy. For He- Ne laser, with or without different doses (2.5, 5.0, 10.0 and 20.0 kGy) of γ-irradiation, enzyme induction was significantly stimulated and positively correlated with the dose levels of γ-irradiation in combination with the He-Ne treatment. There was a significant increase in the concentration of MDA and this increase was more pronounced at dose level 20.0 kGy (38.2 μmol/g d.w) compared to the control (3.9 μmol/g d.w). Laser treatment by He-Ne laser or diode laser only caused a slight increase (P<0.05) in MDA content (4.4 and 5.08 μmol/g d.w respectively) compared to the control (3.9 μmol/g d.w). H2O2 content significantly increased in all treatments and this increase reached its maximum at dose level 20.0 kGy (36.3 μmol/g d.w) compared to the control (2.3 μmol/g d.w.). On the other hand, He-Ne or diode laser treatments combined with γ-irradiation significantly decreased in comparison with γ-irradiation treatments alone. In the case of glutathione content, there were significant increases by γ-irradiation at dose levels 2.5, 5.0, 10.0 and 20.0 kGy. Furthermore, with a combination of γ-irradiation and He-Ne or diode laser, a marked increase in glutathione content was found and was more pronounced than that of gamma irradiation alone.