CALLASE-(1,3-BETA-D-GLUCANASE) ACTIVITY DURING SPRING REACTIVATION IN DECIDUOUS TREES

The activity of callose-degrading enzyme endo-1,3-beta-D-glucanase (EC 3.2.1.39) was studied in tissue composed of cambium- and secondary phloem cells of goat willow (Salix caprea), sycamore maple (Acer pseudoplatanus), and european ash (Fraxinus excelsior) from January to May in 1989 and 1990, in relation to bud development in spring. Extracts were assayed colorimetrically for 1,3-beta-D-glucanase activity by using a dye-substituted pachyman derivative as substrate. The pH optimum of glucanase activity in maple and ash was almost identical (6.0-6.5), whereas that of willow appeared to be in the acidic range (3.5-4.0). In general there seems to be a trend that glucanase activity rises in early spring consistent with it playing a role in dissolution of callose before bud break. An atypical early rise of glucanase activity in ash and maple in 1989 is probably explained by unusually high temperatures in January.