ETHYLENE AND POLYAMINE METABOLISM IN CLIMACTERIC AND NONCLIMACTERIC CARNATION FLOWERS

We have compared the ethylene and polyamine metabolism of senescing flowers from two cultivars of carnation (Dianthus caryophyllus L.), one showing climacteric ('Arthur') and the other nonclimacteric behavior ('Killer'). 'Arthur' carnations showed the first symptoms of senescence at day 7, coinciding with maximum ethylene and CO2 production, a peak in the ethylene-forming enzyme (EFE) activity, and a 7-fold increase in free ACC content in respect to the initial value. In 'Killer' carnations, however, onset of senescence was 15 days after harvest, and no ethylene or CO2 peak was detected. The lack of ethylene production was due to a constantly low level of free ACC and a low EFE activity. Free polyamine distribution was similar in the two cultivars at the preclimacteric stage, with the spermidine content being about three times that of putrescine. But as senescence progressed, this situation was reversed in 'Arthur' carnation, with a predominance of putrescine during the senescence, while it was maintained in 'Killer', with no significant changes during senescence. No free spermine was found at any stage of senescence in either cultivar. Thus, a correlation exists between ACC level, distribution of polyamines, and longevity of cut carnation flowers. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).