THE INFLUENCE OF WATER AND NUTRIENT DEFIC IENCY ON EPICUTICULAR WAXESOF KOHLRABI LEAVES

The influence of water and nutrient deficiency on amount and micromorp hology of epicuticular waxes was investigated under controlled conditi ons in kohlrabi plants (Brassica oleracea var. gongylodes L.) grown in sand culture. The control was supplied with a nutrient solution accor ding to plant demands. The treatment groups were provided with an amou nt of 50% or 25%, respectively, of the control. A significant reductio n of both mineral element concentration in the leaf tissue and vegetat ive growth was established in the plants of the treatment groups six w eeks after the beginning of the experiment. Micromorphology of epicuti cular waxes as investigated by scanning electron microscopy did not sh ow any distinct changes between control and treatments. Susceptibility of plant material to Botrytis cinerea infection was slightly increase d when water and nutrient supply was reduced by 50%, as established in a leaf disc system. However, content of epicuticular wax remained unc hanged as compared to the control. Further reducing the amount of nutr ient solution to 25% of the control resulted in the susceptibility of leaf discs to B. cinerea decreasing to the level of the fully supplied plants. This is mainly explained by the significantly higher amount o f epicuticular waxes in leaves of this treatment group.