Boronia heterophylla vase life is influenced more by ethylene than by bacterial numbers or vase solution pH

Abstract

Bacterial proliferation in both vase solutions and in cut flower stems has been implicated in reducing the vase life of numerous genera. Boronia heterophylla F. Muell. (Red Boronia) vase life was assessed at two stages of floral maturity for nine vase solution treatments covering a pH range of 2.5–5.7. Vase life for advanced harvest maturity stems ranged from 4.2 d in 10mM citric acid+50mgL−1 chlorine (pH 2.5) to 12.9 d after STS pulsing (pH 5.7). For normal harvest maturity stems, the corresponding range was 5.8–19.0 d, respectively. Vase solutions containing 50mgL−1 chlorine biocide resulted in decreased longevity. In contrast, pulsing with the ethylene-binding inhibitor, STS, significantly increased vase life. The number of bacteria in the vase solutions after 11 d was determined in stems of advanced maturity. The solution with the greatest number of bacteria, 4.0×1010cfumL−1, was water used after STS pulsing and in which the flowers lasted longest. Vase solution bacteria were enumerated on days 0, 3, 6, 9 and 12 of the vase period with stems of normal harvest maturity. There was no relationship between vase life and vase solution bacterial numbers (R¯2=0.000). Moreover, there was a negative relationship between numbers of bacteria in basal 0–5cm stem segments and vase life. As no correlations were evident between longevity and either the pH or vase solution bacterial numbers, B. heterophylla vase life was evidently limited principally by ethylene action.