THE MODE OF ACTION OF BACTERIA IN THE VASCULAR OCCLUSION OF CUT ROSE FLOWERS

In cut flowers water uptake is diminished by the development of occlusion in the stems. There are two main causes of this occlusion; microorganisms and an effect related to storage of the stems in air.

The mechanism of action of microorganisms was found to be probably largely due to bacteria, rather than fungi or yeasts. Stem occlusion by a suspension containing a high number of bacteria (5 x 10⁹ colony forming units/ml) was found to occur within 30, min which is too rapid for a physiological response. The occlusion also developed when stems are placed in a suspension of bacteria inactivated by a heatshock (15 min, 70 °c) or by sterilization (15 min, 121 °C). The occlusion, therefore, does not depend on the action of living bacteria. Slime isolated from bacterial colonies also resulted in vascular occlusion. A specific effect of enzymes was investigated by comparing the effect of cellulase (about 50 kD) with inert albumin also of about 50 kD. Both resulted in the same occlusion. It is concluded that the occlusion related to bacteria may be partially due to the molecules released by the bacteria.