THE REGULATION OF LIGHT INTENSITY ON LEAF ANTIOXIDATIVE ABILITY IN FOUR SUBTROPICAL FOREST SPECIES
光照强度调控4种亚热带森林植物叶片的抗氧化能力

The antioxidative ability of four subtropical forest plants, Schima superba , Castanopsis fissa (tree species), and Psycotria rubra,Ardisia quinguegona (shrub species) growing under different light intensities was studied. Potted seedlings were grown in three light treatments: natural sunlight (100%), and shading to 36% and 16% of natural sunlight. Young trees growing in natural forest in deep shade (8% and 3% sunlight) and at an artificially open site(sparsely cut) were also tested. Changes in the contents of ascorbic acid (AsA), glutathione (GSH) and the activities of ascorbate peroxidase (APX), superoxide dismutase (SOD) were analyzed in leaves sampled in summer and winter. Under natural light conditions, the two shrub species showed higher antioxidative ability, with a high amount of AsA and high activities of APX, SOD relative to the tree species. The levels of AsA, GSH, APX and SOD decreased with declining light intensity in four species, but the antioxidative ability response to changing light intensity was greater in the shrub species. A close positive correlation between AsA, APX and SOD was observed across changing light intensities, indicating a good coordination of antioxidative metabolism in these woody plants. The results were somewhat different in summer and winter,showing that in addition to the important role of light intensity, other environmental factors, such as temperature may also be involved in the development and regulation of plant antioxidative ability.