Abstract
Seasonal changes in peroxidase activity in the procambium of Salix buds were elucidated by cytochemical methods combined with transmission electron microscopy. Three different substates were used, viz. diaminobenzidine (DAB), tetramethylbenzidine (TMB), and p‐phenylenediamine (PPD) + pyrocathecol (PC). The specificity of the reactions was tested with the aid of several inhibitors: sodium diethyldithiocarbamate (DDC), KCN, and 3‐amino‐1,2,4‐triazole (AT, inhibitor of catalase), and by exclusion of H2O2. Peroxidase activity was found mainly in the middle lamella region of the walls, at the plasmalemma, in the ER, nuclear envelopes, and many small vesicles (possibly lysosomes). The results indicate the presence of many isoenzymes with various pH optima and sensitivity to inhibitors. The enzyme activity was highest during dormancy (autumn and winter), perhaps a component of the hardening process. It decreased considerably in the spring simultaneously with dormancy breaking.
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