Light conditions exert direct effects on metabolism, growth and development of plants, including their ability to defend against pests. In this study, we explored the impact of light conditions on response of six understory shrub species (Sambucus nigra, Prunus serotina, Prunus padus, Cornus sanguinea, Frangula alnus and Corylus avellana) to grazing by herbivore insects. Shrub species differed significantly in the level of foliar perforation by insects. Except for C. avellana, leaves of plants exposed to full sun were less affected by leaf-chewing insects than leaves from plants grown in low light. It is likely that shade-grown plants have higher host quality due to their lower content of secondary metabolites (soluble phenols and condensed tannins) and higher content of nonstructural carbohydrates and nitrogen. However, there were no significant relationships between interspecific susceptibility to grazing and leaf chemistry, indicating that other factors such as combined effect of host defense and herbivore abundance may be responsible for observed differences in foliar perforation.

47-57