Vessel differentiation in isolated stem segments of Fraxinus excelsior L. after treatment with auxin

Experiments were carried out on isolated stem segments of ash collected from natural conditions during the winter dormancy season. In order to stimulate cambial activity and vessel differentiation the internodes were treated with auxin. The duration of treatment with auxin was different in the particular experimental variants. It appeared that auxin was necessary not only for induction of vessel differentiation but also during their maturation. The results are discussed on the basis of S a c h s' (1981) hypothesis.