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.
Recent publications
Strengbom J, Witzell J, Nordin A and Ericson L. : Do multitrophic interactions override N fertilization effects on Operophtera larvae? Oecologia (in press)
Nordin A, Strengbom J, Witzell J, Näsholm T and Ericson L : Nitrogen – a threat to biodiversity of boreal forests. AMBIO 34:20-24.
Witzell J, Karlsson M, Torp M and Wingsle G. : Transgenic hybrid aspen with altered defensive chemistry – a model system to study the chemical basis of resistance? In: Rusts on Poplars and Willows (Pei M and McCracken A eds.) CABI publishings.
Witzell J, Shevtsova A. : Nitrogen-induced changes in phenolics of Vaccinium myrtillus: implications for interaction with a parasitic fungus. J Chem Ecol 10:.
Strengbom J, Olofsson J, Witzell J, Dahlgren J : Effect of repeated damage and fertilization on plant palatability to grey sided voles, Clethrionomys rufocanus. OIKOS 103:133-141.
Witzell J, Gref R, Näsholm T : Phenolic compounds in vegetative tissues of bilberry (Vaccinium myrtillus L.) Biochem Syst Ecol 31(1):115-127.
Submitted manuscripts
Witzell J, Kuusela T, Sarjala T: Polyamine profiles of healthy and parasite-infected Vaccinium myrtillus plants under nitrogen enrichment
Stenberg J, Witzell J and Ericson L. Past history of coexistence reveals symmetric coevolution between a host plant and its specialist leaf beetle herbivores
Selected earlier publications
Hakulinen J , Julkunen-Tiitto R : Variation in leaf phenolics of field-cultivated willow (Salix sp.) Clones in relation to occurrence of Melampsora rust. For Path 30:29-41.
Hakulinen J, Sorjonen S, Julkunen-Tiitto R : Leaf phenolics of willow clones differing in resistance to Melampsora rust. Physiol Plant 105: 662-669.
Hakulinen J : Nitrogen-induced reduction in leaf phenolic level is not accompanied by increased rust frequency in a compatible willow (Salix myrsinifolia)-Melampsora rust interaction. Physiol Plant 102:101-110.
Hoffland, E., Hakulinen, J. and Van Pelt, J.A. : Comparison of systemic resistance induced by avirulent and non-pathogenic Pseudomonas species. Phytopathology 86:757-762.
Hakulinen J, Julkunen-Tiitto R and Tahvanainen J : Does nitrogen fertilization have an impact on the trade-off between willow growth and defensive secondary metabolism? Trees 9:235-240.
