2,4-Pyridinedicarboxylic Acid Prolongs the Vase Life of Cut Flowers of Spray Carnations

2,4-Pyridinedicarboxylic acid (PDCA) is a structural analog of 2-oxoglutarate and has been shown to inhibit 2-oxoglutarate-dependent dioxygenases by competing with 2-oxoglutarate, and ethylene production in detached carnation flowers by competing with ascorbate on 1-aminocyclopropane-1-carboxylate (ACC) oxidase action. In the present study, the inhibition of ACC oxidase action by PDCA was confirmed with a recombinant enzyme produced in Escherichia coli from carnation DcACO1 cDNA. PDCA had various effects on ethylene production in cut ‘Light Pink Barbara (LPB)’ carnation flowers; ethylene production was accelerated or delayed in some flowers, whereas it did not change in others as compared to untreated control flowers. This varied action of PDCA may be caused by its possible combined actions; that is, inhibition of ACC oxidase action as well as its action on unidentified biochemical processes which use 2-oxoglutarate as a co-substrate, such as the biosynthesis and inactivation of gibberellins. Meanwhile, PDCA treatment significantly prolonged the vase life of bunches of cut ‘LPB’ carnation flowers; the magnitude of the extension of vase life was 53, 111, and 135% at 0.3, 1, and 2 mM PDCA, respectively, as compared with the non-treated control. Also, PDCA lengthened the vase life of ‘Mule’ carnation flowers. The present findings suggest the potential of PDCA as a preservative for cut flowers of spray carnations.