CHANGES IN LIPID-PEROXIDATION AND ANTIOXIDANTS CONTENT IN COTYLEDONS OF JAPANESE RADISH

The relationship between senescence of cotyledon of Japanese radish an d changes in levels of antioxidants was investigated by monitoring the levels of malondialdehyde (MDA), chlorophyll (Chl), ascorbic acid (As A), alpha-tocopherol (alpha-Toc) in cotyledons, and the percentage of electrolyte leakage from cotyledonary discs. The content of MDA, which reflects lipid peroxidation, increased 3 days after sowing parallelin g the increase in electrolyte leakage and Chl loss. alpha-Toc content increased linearly 2 to 10 days after sowing, whereas the AsA content increased rapidly, reaching a maximum 3 days after sowing and decreasi ng thereafter. An increase in MDA was accompanied by a concomitant dec rease in AsA content. The AsA content increased significantly when the cotyledonary discs were administered L-galactono-1, 4-lactone, an imm ediate precursor of AsA, which suppressed changes in MDA and Chl conte nts. These results suggest that AsA has an important role for suppress ion of lipid peroxidation and Chl loss in cotyledons of Japanese radis h.