INDUCED DEFENSE REACTION IN THE PHLOEM OF SPRUCE (PICEA-ABIES) AND LARCH (LARIX-DECIDUA) AFTER ATTACK BY IPS-TYPOGRAPHUS AND IPS CEMBRAE

The physiological reaction of larch (Larix decidua) and spruce (Picea abies) after attack by lps cembrae and lps typographus, respectively, was investigated from 1991 until 1993 by analysis of the constituents of phloem tissue (soluble carbohydrates, protein amino acids, pinitol, shikimic acid, quinic acid, catechin, procyanidines). To exclude beha vioural artefacts, the investigation was performed under natural field conditions with free choice of their host by both bark beetle species . A sequence of resistance mechanisms was detected after attack. Depen dent upon the intensity, the duration, and the success of the attack a t first locally limited changes in the metabolism of attacked trees oc curred. These changes resulted in a deterioration in the food quality (shift of the nutrient/inhibiting compounds ratio in favour of the lat ter) with the effect of disturbing the establishment of the beetles. W ith stronger and longer lasting attack, long-lasting systemic changes in the metabolism of the whole tree were induced. These resulted, like wise, in a deterioration of the nutrient/inhibiting compounds balance, an increase of the protein biosynthesis and an intensification of the defence metabolism. This reaction was sustained with successful attac k until the end of the development of the brood beetles. Thus, the ind uced resistance reactions were directed against the parent generation and the brood alike, extending from the level of the individual tree t o the level of the population of trees.