DISTRIBUTION AND VARIATIONS OF POTASSIUM AND CALCIUM IN DIFFERENT CROSS-SECTIONS OF PICEA-ABIES (L) KARST NEEDLES AND FAGUS-SYLVATICA (L) LEAVES EXPOSED TO OZONE AND MILD WATER-STRESS

Two clones of 8-year-old Norway spruce trees, and beech trees, planted directly into the soil in open-top chambers, were exposed to elevated ozone concentrations and subjected to a mild soil drought stress. The nutrient partitioning and intertreatment differences in nutrient leve ls were studied. in elevated ozone, both clones had increased potassiu m and calcium levels, whereas in beech, ozone-treated trees had decrea sed potassium levels. Drought caused decreases in these nutrients for all species. The effect of combining the 2 stresses was more complex, however, and the previously observed effects were not obtained in all cell tissues. Furthermore, they showed both interspecific and interclo nal differences. The hypothesis that ozone affects the root nutrition and cell membrane permeability is discussed.