¹⁴C₂H₄: Its Incorporation and Oxidation to ¹⁴CO₂ by Cut Carnations

Abstract

Cut carnations (Dianthus caryophyllus L. cv. `Improved White Sim') were exposed to ultra high purity ¹⁴C₂H₄ (20 μl/1) during flower opening and senescence to study its incorporation and metabolism. During treatment precautions were taken to exclude inhibitory volatiles from rubber serum stoppers which were identified as CS₂ and COS. As with the pea seedling (Nature 1975, 255:144-147), cut carnations incorporated ¹⁴C₂H₄ into ethanol-soluble tissue metabolites and oxidized the hormone to ¹⁴CO₂. Oxidation increased from 0.5 to 3 dpm · mg dry wt⁻¹·6 hr⁻¹ during the period of flower opening and early petal wilt. As severe petal wilt set in, and the ovary increased in size and dry weight, oxidation increased to a peak of nearly 29 dpm · mg dry wt⁻¹·6 hr⁻¹. Concomitant with this peak was a similar rise in the rate of ¹⁴C₂H₄ incorporation into the petals, peduncle, bracts, and sepals. Much higher rates of incorporation were found for the reproductive and receptacle tissues. Incorporation into these tissues steadily increased during flower opening reaching a peak of over 160 dpm · mg dry wt⁻¹ · 6 hr⁻¹ just before full bloom. This peak preceded a peak of endogenous ethylene production while the ¹⁴C₂H₄ oxidation peak followed it.