Anatomy of abscission zone of Betula pendula (Roth.) leaves from trees growing under different levels of pollution

A study was carried out on the leaf abscission zone from birch trees growing on polluted sites (two) and a non-polluted site (one). Samples for anatomical investigation were collected from six trees on each site, during three succeeding vegetation seasons. It was observed that in trees growing at the polluted sites: 1) maturation of the abscission zone was faster, 2) the protective layer was thinner and 3) the formation of leaf scar periderm was delayed in comparison with trees from the non-polluted site. The results obtained suggest that environmental pollution influences the formation of the abscission zone and the protection of the leaf scar.