Effects of La~(3+) on the Active Oxygen-Scavenging Enzyme Activities in Cucumber Seedling Leaves

摘要

The effects of La~(3+) on the antioxidant enzyme activities and the relative indices of cellular damage in cucumber seedling leaves were studied. When cucumber seedlings were treated with low concentrations of LaCl_3 (0.002 and 0.02 mM), peroxidase (PO) activity increased, and catalase (CAT) activity was similar to that of control leaves at 0.002 mM La~(3+) and increased at 0.02 mM La~(3+), whereas superoxide dismutase (SOD) activity did not change significantly. The increase in the contents of chlorophyll (including chlorophylls a and b), carotenoids in parallel with the decrease in the level of malondialdehyde (MDA) suggested that low concentration of La~(3+) promoted plant growth. However, except the increase in SOD activity at 2 mM La~(3+), CATand PO activities and the contents of pigments decreased at high concentrations of La~(3+) (0.2 and 2 mM), leading to the increase of MDA content and the inhibition of plant growth. It is suggested that lanthanum ion is involved in the regulation of active oxygen-scavenging enzyme activities during plant growth.