We studied the activity of apoplastic (ApIn), vacuolar (VacIn), cytoplasmic (CtIn) invertases and sucrose synthase (SS) in trunk tissues of curly birch trees with figured and straight grain over the growing season. ApIn activity in phloem tissues was higher compared with other enzymes that break down sucrose. Its values were the highest in May and during the plants' preparation for dormancy. During high cambium activity and secondary cell wall formation ApIn activity in the phloem dropped significantly. In this period, SS activity in the xylem grew notably. Differences in the distribution of enzyme activity were found between curly birch trees with figured trunk wood and the plants with no abnormalities. Abnormal sections featured high ApIn activity throughout the growing season. In plants with normal wood texture, the sucrose synthase pathway of sucrose metabolisation prevailed during active growth over the invertase pathway.