Effects of UV Radiation on Pigment Contents and Antioxidative Enzyme Activities in Leaves of Cattleya and Cymbidium Orchid Plants

Abstract

Cattleya (Sophrolaeliocattleya Estella Jewel 'Kazumura') and Cymbidium (Cymbidium Sazanami 'Harunoumi') orchids were grown under strong and weak solar UV radiation for 80 days from August 1 to test the effects of radiation on foliar pigment contents and antioxidative enzyme activities in two-year-old leaves. Foliar chlorophyll and carotenoid contents in both Cattleya and Cymbidium leaves grown under strong UV radiation were lower than those under weak UV radiation. Flavonoid content in Cattleya leaves grown under strong UV radiation was also lower than that under weak UV radiation, but that in Cymbidium leaves grown under strong and weak UV radiation was the reverse. Activities of ascorbate peroxidase after 10 days and catalase from 20 to 40 days in Cattleya leaves exposed to strong UV radiation were higher than those grown under weak radiation. In contrast, activities of superoxide dismutase and catalase after 20 days in Cymbidium leaves grown under strong UV radiation were lower than those of leaves exposed to weak radiation. Thus, our results revealed that the intensity of UV radiation differently affected the leaves of antioxidative substances and enzymes activities of the two orchid species.