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 decreased as aging progressed. Total thiol content followed the alpha-tocopherol pattern during aging. Petals' ascorbic acid content started to decline 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 treatment. Paraquat exposure did not significantly modified the activities of glutathione reductase and catalase, but superoxide dismutase activity was increased. alpha-Tocopherol content was not affected by paraquat, but total thiols content decreased by 50%. Flowers showing browning that involved 50-100% of the petal, were exposed to 1 mM paraquat over 24 h. The activities of superoxide dismutase, glutathione reductase, and catalase were not affected. Paraquat exposure led to a 3-fold increase in oxygen radical generation, and to a 59% increase in hydroperoxide content in aged petals. The data presented here suggest that oxidative stress and a concerted antioxidant response are associated with the initial stages of aging in Dendranthema morifolium petals. (C) 1997 Elsevier Science Ireland Ltd.