Effect of paraquat on the antioxidative enzyme activities and lipid peroxidation in opium poppy (Papaver somniferum L.)

Abstract

Changes of malondialdehyde (MDA) content, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in opium poppy, Papaver somniferum were measured at the bud stage treated with different concentrations of paraquat. The results showed that the changing rate of MDA content was the same as that of the cell membrane electrolyte leakage. The MDA content and cell membrane electrolyte leakage decreased in the early stage then increased under 3 ml l–1, 6 ml l–1, 12 ml l–1 treatment. In contrast, the MDA content and relative membrane permeability increased in the early stage then decreased under 24 ml l–1 treatment. Antiox-idant enzyme activities varied under different treatments. SOD activities decreased during 3–24 h and then increased under the 24 ml l–1 treatment. All the peaks of POD activities appeared at the 3 h post treatment. POD activities at the 9 h and the 36 h under 24 ml l–1 treatment were significantly lower than in the control. CAT activities varied under different treatments, increased at 9 h and decreased at 36 h post treatment under 24 ml l–1 treatment. This means that the active oxygen produced in the leaf cells of opium poppy was beyond the recovering capacity of antioxidant enzyme, resulting in the damage of enzyme. These results suggest that a high concentration (24 ml l–1) paraquat treatment caused damages by speeding up the peroxide of the opium poppy plant cells, whereas lower concentrations were less effective.