CAMBIAL ACTIVITY, AN ACTIVE OR PASSIVE CO MPONENT IN THE TREES GROWTHREACTIONS

The shortcomings of old and recent theories about cambial activity con trol, in the whole tree, are stressed. The gap between those conceptio ns mainly stems from the fact that, in terms of hormonal regulation, t he cambium is often seen as dependent an the primary growth. Several e xamples are exposed where a relative autonomy appears either of the ca mbial activity itself or of the parenchymatous structures that it prod uces. These examples refer to correlations between shoots, stem form a nd mechanical constraints, and mobilisation or storage of reserve suga rs. A hypothesis is proposed explaining how parenchymas acting as a si nk might contribute to induce growth cessation. The question of the pl ace of cambium and its products in the general ''economy'' of tree dev elopment is thus raised.