Effect of local heating and cooling on cambial activity and cell differentiation in the stem of Norway spruce (Picea abies).

Unlabelled: BACKGROUND AND AIMS The effect of heating and cooling on cambial activity and cell differentiation in part of the stem of Norway spruce (Picea abies) was investigated.

Methods: A heating experiment (23-25 degrees C) was carried out in spring, before normal reactivation of the cambium, and cooling (9-11 degrees C) at the height of cambial activity in summer. The cambium, xylem and phloem were investigated by means of light- and transmission electron microscopy and UV-microspectrophotometry in tissues sampled from living trees.