Wound-induced oxidative responses in mountain birch leaves.

OBJECTIVE

The aim of the study was to examine oxidative responses in subarctic mountain birch, Betula pubescens subsp. czerepanovii, induced by herbivory and manual wounding.

METHODS

Herbivory-induced changes in polyphenoloxidase, peroxidase and catalase activities in birch leaves were determined. A cytochemical dye, 3,3-diaminobenzidine, was used for the in situ and in vivo detection of H2O2 accumulation as a response to herbivory and wounding. To localize peroxidase activity in leaves, 10 mm H2O2 was applied to the dye reagent.

RESULTS

Feeding by autumnal moth, Epirrita autumnata, larvae caused an induction in polyphenoloxidase and peroxidase activities within 24 h, and a concomitant decrease in the activity of antioxidative catalases in wounded leaves. Wounding also induced H2O2 accumulation, which may have both direct and indirect defensive properties against herbivores. Wound sites and guard cells showed a high level of peroxidase activity, which may efficiently restrict invasion by micro-organisms.

CONCLUSIONS

Birch oxidases together with their substrates may form an important front line in defence against herbivores and pathogens.