Biotrophic fungal interaction with host plants involve alterations in host metabolism in favour of the fungus, characteristic of perturbations in the levels of plant growth regulators. Pyrenopeziza brassicae mycelia, culture filtrate and spore extracts contained zeatin riboside and iso-pentenyladenisine-type cytokinins as determined using HPLC-ELISA. The significance of cytokinin synthesis by P. brassicae in relation to infection of host plant tissue is discussed.

Tissue specific localization of soluble secondary metabolites was demonstrated in ectomycorrhizae and uninfected roots of Picea abies, Larix decidua, Pinus sylvestris and Abies alba. Compounds were analysed by HPLC and by histochemical methods. Specific distribution and age-dependent changes were observed with several metabolites. For catechin corresponding patterns were found within the cortex of all investigated conifers. Levels of this metabolite were highest within the apical cortex cells and decreased on aging of the tissue. In spruce contents of catechin showed evident seasonal changes. Stilbene glucosides were detected within the pericycle of spruce roots and as well the phloem tissue of larch with levels increasing during root development. In larch two anthocyanins accumulated in the calyptra. In older tissues of larch roots larixin-glucosid and quercetin-rhamnosid were detected, the latter with highest levels in the phloem tissue. For cell wall bound ferulic acid increasing levels could be found concomitant with the development of the root.

It is often difficult to predict how synergistic effects work and how dieback may be expected to spread through an area over time. On the other hand concepts and methods for compensation of acid deposition, melioration and restauration of acidified forest areas represent a major management problem. The following examples show how GIS may be used to find answers to these questions.

The article presents a state of art of forest decline inventories in Slovenia. The first part deals with methodological and technological aspects of forest health inventories, while the second one describes some hints and directions of further forest inventories development.

The Forest Research Plot was chosen on a typical site for the Pokljuka plateau. It is covered by a supposedly autochthonous old Norway spruce stand with rejuvenation centres. Data on the physiological parameters can be used as representation values for a subalpine Norway spruce stand. The studies include: standard site and dendrological parameters, physiological parameters (foliar analysis, antioxidants, hormones and aminoacids in spruce needs), genetical and biochemical analysis (isoenzymes and molecular markers), microbiological activity (acid phosphatase, rate of decomposition, number and occurrence of fungal decomposers of wood and litter) and studies of symbionts and pathogens of Norway spruce (mapping of fruitbodies of mycorrhizal fungi, types of ectomycorrhizae, endophytes, epiphytes - lichens and phytopathological surveys). All physiological and ecological studies are planned to be repeated at certain time periods in order to understand better the functioning of the forest ecosystems on Pokljuka.

First studies of this kind were based on mapping of cover and frequency of crustose, foliose and fructicose epiphytic lichens on trees which were assessed also for the decline symptoms. Since 1985 epiphytic lichen vegetation has been assessed by this methods and results, expressed as a lichen map of Slovenia were used as an air quality indicator for plots of forest die-back inventory. In case studies of forest decline, in collaboration with lichenologist from Graz Univ., Austria, all epiphytic lichen species were mapped in order to obtain better measure of air quality in the area studied. Very polluted and still clean and well preserved forests were investigated. From the material collected and determined a lichen herbarium has been established on the Slovenian Forestry Inst.. Possibilites of further research and use of epiphytic lichens as air quality indicators are discussed.

Cytokinins were analysed by a combined HPLC-ELISA method in needles of Norway spruce seedlings. The seedlings were grown in vitro on sterile or nonsterile soil substrates from two differently polluted forest research plots. Difference were predominantly found in the isopentenyladenine-type of cytokinins. These were elevated in seedlings, grown on polluted soils in comparison to those, grown on soils from the unpolluted plot. A possible explanation might be in the change of the metabolism in the roots due to pollution stress (when grown on sterilized substrates) or in change of the mycorrhizosphere organisms (when grown on nonsterile soil substrates). The model system using Norway spruce seedlings as tester organisms for soil pollution is discussed.

Root-induced changes in the rhizosphere and root colonization with mycorrhizal fungi have marked influence on mineral nutrient acquisition from soils. Enhanced exudation of organic acids under phosphorus deficiency is a widespread phenomena in woody species forming root clusters. Root colonization with endomycorrhizas (AM) and ectomycorrhizas (ECM) increases the spatial availability of nutrients in the soil and enhances plant growth particulary on nutrient-poor soils. Most of these studies have been conducted under controlled environmental conditions and with annual plant species mycorrhizal with AM. Conclusions on the role of ECM colonization for nutrient acquisition of trees in forest stands are not possible at the present state of knowledge.

The condition of silver fir (Abies alba Mill.) trees was monitored 1988-1994 by measuring electrical resistance of living tissues at breast height. Slime cells in bark and traumatic resin canals in wood were investigated as possible symptoms of silver-fir decline.