Abstract: Spinach ( Spinacia oleracea Mill. ) cultivar "Huabo No. 1" was grown in an indoor environment and treated with 13.0 kJ' m-1. d-1 of ultraviolet-B (UV-B 280 to 320 nm) to study the effect of UV-B irradiation on flavonoids and lipid peroxidation in spinach leaves. The results showed that enhanced UV-B irradiation decreased the leaf fresh weight and the content of soluble protein and chlorophyll, and induced large accumulation of UV-absorbing flavonoids in the leaves. UV-B irradiation also promoted the production of superoxide radicals (O2-) and malondialdehyde in spinach leaves. However, the ascorbic acid (ASA) level was decreased under UV-B treatment. It was interesting that high peroxidase (POX), superoxide dismutase (SOD) and catalase (CAT) activities in spinach leaves were induced by UV-B irradiation, the former two being more sensitive. It was suggested that UV-B induced the accumulation of O2- resulting in the lipid peroxidation and in mm inhibiting the growth of spinach. However, the increase of UV-absorbing flavonoids and anti-oxidative enzymes induced by high accumulation of 02- could not reverse the process of UV-B damage.

Key words: Spinach, Ultraviolet-B, Flavonoids, Lipid peroxidation, Anti-oxidative enzymes