Prolonged influence of short pulses ultraviolet-C radiation on young pea plant does not alter important antioxidant defense enzyme activities in young leaves.

摘要

The behavior of the antioxidant defense enzyme activity in the youngest leaves (3rd, 4th or 5th) after exposure of intact pea (Pisum sativum L., cv. Scinado) plants for 10, 14 or 21 consecutive days, to low doses of ultraviolet-C (UV-C) radiation was studied. Two UV-C regimes were used: C1 (20 s d-1, 0.1 kJ m-2 d-1) and C2 (60 s d-1, 0.3 kJ m-2 d-1). Only C1 regime led to a slight increase in hydrogen peroxide (H₂O₂) content after 10 and 14 days of irradiation (20% and 27%, respectively as compared to control). The C2 regime did not induce a noticeable increase in H₂O₂ as compared to C1, suggesting that H₂O₂ could be accepted as a signal for activation of defense responses rather than a stress marker. The activity of superoxide dismutase decreased at the end of the stress programme in C2-irradiated plants. An increase was found in the activities of glutathione-S-transferase (39%, 10 days C2) and glutathione-reductase (23%, 10 days C2; 12%, 14 days C1; 11%, 14 days C2). In conclusion, the activation of the antioxidant defense system seemed negligible when pea plants were exposed to prolonged and short pulses of UV-C radiation, although the possibility of isoenzyme changes could not be excluded and needs additional experiments.