Conceptual models of stress reactions and tolerance in plants have bee
n addressed several times. However, most models rarely consider reacti
on to multiple stress factors or can be related to plant structure. In
this paper, a conceptual model of tree reactions to stress and adapta
tion to stress is presented. The model is based on the morphology and
physiology of trees. In particular the model is based on the concept t
hat any changes in morphology and physiology will have advantages and
disadvantages for particular environmental conditions or pollution env
ironments. Changes in morphology and physiology, in the form of adapta
tion, have a cost to the tree, and will have advantages and disadvanta
ges if a number of stress factors are considered. This conceptual mode
l is presented in the framework of examples from the literature and fr
om the authors own work, and applied to tree reactions and tree adapta
tion to stress. (C)1998 Elsevier Science Ltd.