Carbon-based secondary metabolites, such as phenolic acids, flavonoids and tannins, are frequently implicated in plant defence against biotic and abiotic stresses. The levels of these metabolites vary greatly according to plant inherent factors, and their levels readily respond to changes in environment conditions (e.g., nutrition and light availability). My research is focusing on the role of phenolic compounds in the interactions between forest plants and their natural enemies (pathogens and herbivores). I am interested in genotypic, within-plant and environmentally-induced variation in phenolics, and in the functional integration of phenolic-based defence to plant primary metabolism. The plant species I am working with include Vaccinium myrtillus, V. vitis-idaea, Deschampsia flexuosa, Filipendula ulmaria, Pinus sylvestris and Salicaceae plants (Populus sp., Salix sp.). The general aim of the research is to obtain new information about the regulation and consequences of phenolic-based defence in plants that encounter different stress situations. The results can be useful in predicting the effects of environmental pollutants on boreal forest ecosystem, and they may be applicable in breeding and selection of stress-tolerant plants using traditional breeding or genetic manipulations.