Xylem occlusion in Bouvardia flowers : evidence for a role of peroxidase and catechol oxidase

During vase life, Bouvardia flowers show rapid leaf wilting, especially if they are stored dry prior to placement in water. Wilting is due to a blockage in the basal stem end. We investigated the possible role of peroxidase and catechol oxidase in the blockage in cv. van Zijverden flowers, which were placed, for 5 h at 20 °C, in an aqueous solution containing enzyme inhibitors. Flowers were then stored dry in plastic bags (24 h at 5 °C, 100% RH) and placed in water at 20 °C without recutting the stems. Inhibitors of both peroxidase (hydroquinone, p-phenylene diamine, copper ions) and catechol oxidase (tropolone, 2,3-dihydroxynaphtalene) considerably delayed the time to leaf wilting. It is concluded that the blockage is apparently due to a wounding reaction and that it involves both peroxidase and catechol oxidase activity