PERTURBATION OF WATER-CONTENT AND SURFACE ALTERATION IN NEEDLES OF SPRUCE TREES (PICEA-ABIES L) FROM THE FRENCH JURA ACCORDING TO THEIR AGE AND TO THE HEALTH-STATUS OF THE TREES

Measurements of needle water content and scanning electron microscopy studies of leaf surfaces were carried out on a large number of declining and healthy spruce trees in order to characterize the decline of this species in the French Jura. Variations in water content were closely correlated with the health status of the trees: needles of damaged trees displayed a marked decrease in leaf water content. Moreover, the number and structure of the epicuticular waxes and also the substomatal waxes were modified. At a given age, the needles of declining trees had the same water content as those displayed one year later by needles of the healthy trees. Thus, the decline of spruce trees in the French Jura appears to correspond to an early ageing of the needles.