An Effect of Ethylene on the Distribution of 14C-sucrose from the Petals to Other Flower Parts in the Senescent Cut Inflorescence of Dianthus caryophyllus

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Abstract
The distribution of carbon-14 in the flower parts of the cut carnation inflorescence after feeding 14C-sucrose through the petals was studied during natural ageing and after ethylene treatment. Levels of ethylene which caused irreversible wilting of petals also promoted an accelerated transfer of the radioactive sucrose to the nectar, gynaecium and stem. Since the nectar received a relatively large proportion of the radioactive carbon, the composition of the sugars in the nectar and the vascularization of the nectary were investigated. Sucrose comprised about 85 per cent of the nectar sugars and the balance was glucose and fructose. The vascular tissue closest to the nectary consisted of phloem elements; tracheary elements terminated deeper in the receptacle and were surrounded by a ring of phloem. The percentage of solutes in the nectar was about 18 per cent and increased when the flowering stems were placed in sucrose solutions; the solutes in the nectar were principally sugars. Taken together the results show that the nectary can act as a sink for sucrose and, in the flower at least, that translocation of sucrose takes place in the phloem. The results provide further evidence for the hypothesis that ethylene promotes mobilization of substrate and an efflux of material from petals to the gynaecium, nectar and stem.

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