Effect of antimicrobial compounds on the number of bacteria in stems of cut rose flowers

The presence of chlorine in solution (bleach), a slow release chlorine (DICA), a quaternary ammonium compound (benzalkonium chloride), a hydroxyquinoline compound (HQC), or aluminium sulphate in the vase water decreased the number of bacteria in stems of cut ‘Sonia’roses, with respect to untreated controls. However, when the concentration of the antimicrobial compound was high enough to reduce the number of bacteria in stems (measured after 7 d of vase life) to below the detection limit, the roses showed severe leaf chlorosis and leaf abscission. Benzalkonium chloride resulted in damage at a concentration just enough to reduce the number of bacteria in stems. Effects of HQC, aluminium sulphate, and silver nitrate on the number of bacteria were variable. In experiments in which HQC was relatively ineffective, only one bacterial strain was found in the stem. This strain grew on HQC concentrations as high as 400 mg/l, and was identified as Pseudomonas fluorescens. and accepted 8 June 1989