OXIDANTS AND ANTIOXIDANTS DURING AGING OF CHRYSANTHEMUM PETALS

Aging of petals was accompanied by a 9-fold increase in oxygen radical generation, and a 2-fold increase in the content of oxidized proteins . alpha-Tocopherol content increased at the onset of aging, and decrea sed as aging progressed. Total thiol content followed the alpha-tocoph erol pattern during aging. Petals' ascorbic acid content started to de cline when the flowers were excised. Control petals were exposed to 1 mM paraquat during 24 h and neither the production of oxygen radicals nor the content of hydroperoxides were significantly affected by the t reatment. Paraquat exposure did not significantly modified the activit ies of glutathione reductase and catalase, but superoxide dismutase ac tivity was increased. alpha-Tocopherol content was not affected by par aquat, but total thiols content decreased by 50%. Flowers showing brow ning that involved 50-100% of the petal, were exposed to 1 mM paraquat over 24 h. The activities of superoxide dismutase, glutathione reduct ase, and catalase were not affected. Paraquat exposure led to a 3-fold increase in oxygen radical generation, and to a 59% increase in hydro peroxide content in aged petals. The data presented here suggest that oxidative stress and a concerted antioxidant response are associated w ith the initial stages of aging in Dendranthema morifolium petals. (C) 1997 Elsevier Science Ireland Ltd.