14C2H4 Metabolism in Morning Glory Flowers

Abstract

Flowers of Ipomoea tricolor Cav. (cv. Heavenly Blue) were cut at various stages of development and evaluated for their ability to metabolize ethylene. Freshly cut buds or flowers were treated in glass containers for 8 h with 6 .mu.l/l of highly purified 14C2H4. Following removal of dissolved 14C2H4, radioactivity was determined for the different flower tissues and trapped CO2. 14C2H4 oxidation to 14CO2 and tissue incorporation occurred at very low to nondetectable levels 2-3 days prior to flower opening. About 1 day prior to full bloom, just at the time when mature buds become responsive to ethylene, there was a dramatic increase in the capacity of the buds to oxidize 14C2H4 to 14CO2. This activity continued to increase until the flower was fully opened reaching a peak activity of 2500 dpm [disintegrations per minute] per 3 flowers per 8 h. It then declined as the flower closed and rapidly senesced. A similar but smaller peak occurred in tissue incorporation and it was followed by a second peak during late flower senescence. This first peak in tissue incorporation and the dramatic peak in ethylene oxidation slightly preceded a large peak of natural ethylene production which accompanied flower senescence. The ethylene metabolism observed was clearly dependent on cellular metabolism and did not involve microorganisms since heat killing destroyed this activity and badly contaminated heat-killed flowers were unable to metabolize ethylene.