SEASONAL-CHANGES IN THE AXIAL DISTRIBUTION OF PEROXIDASE-ACTIVITY IN THE XYLEM SAP OF BEECH (FAGUS-SYLVATICA L) TREES

Xylem sap was collected from trunk segments of adult beech (Fagus sylv atica L.) trees by water displacement. Peroxidase activity was analyze d in xylem saps collected in different phases of the yearly growth cyc le and from different heights up the trunks (up to 14 m). The xylem sa ps contained two major peroxidase isozymes with acidic isoelectric poi nts of 4.1 and 4.6, respectively. Mean peroxidase activity was low dur ing the emergence of the new leaves and high in summer and in winter. In the cold season, peroxidase activity decreased from the stem base t o the top, whereas significant gradients were not observed during the vegetative period.