DEVELOPMENT OF ANNUAL XYLEM RINGS AND SHOOT GROWTH OF YOUNG BEECH (FAGUS-SYLVATICA L) GROWN IN SOIL WITH VARIOUS CD AND ZN LEVELS

In a pot culture experiment two-year-old beech (Fagus sylvatica L.) were planted in soil amended with different concentrations of Cd and Zn or combinations of both. Concentrations ranged up to ca 180 mumol Cd and 7500 mumol Zn kg-1 soil dry weight (1 M ammonium acetate extracts). After 2 seasons of growth plants were harvested. Annual xylem growth rings in stems were significantly smaller at 50 mumol Cd kg-1 and 1000 mumol Zn kg-1 as compared to controls. Elongation of apical shoots was significantly reduced at 180 mumol Cd kg-1 and 1000 mumol Zn kg-1. The lowest treatment of 50 mumol Zn kg-1 caused no significant growth depressions of stem diameter and shoot elongation. In the second year of treatment growth reductions were generally more pronounced than in the first season. Uptake and translocation of Cd and Zn into stem wood and leaves were marked and were correlated with substrate concentrations. The observed growth reductions are discussed with respect to possible adverse effects of trace elements on forest trees under field conditions.