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Summary. Mountain birches are deciduous trees consisting of several clonal and partly autonomous ramets. Autumnal moth, Epirrita autumnata, is an extremely harmful pest of mountain birches that during outbreak years may cause the death of trees over large areas.
During the larval development of E. autumnata, leaf characters and nutritional suitability vary considerably both temporally and spatially among and within mountain birches.
Compared to variation between trees, however, the extent of within-tree variation is known for only a limited number of potentially
defensive traits. Plant oxidases, polyphenoloxidases (PPOs) and peroxidases (PODs) may play an important part in dictating
the suitability of a tree for plant-eating animals, including E. autumnata. In this study, we observed changes in the activities of oxidative and antioxidative enzymes along leaf development during
the larval period of E. autumnata. We also estimated the relative amounts of spatial variation among and within trees. Our results show that POD activities
were remarkably high during the rapid elongation growth phase of leaves but decreased with leaf maturation. Thus PODs are
suggested to take part in leaf elongation growth. Time and within tree variation accounted for the most of variation in POD
activities whereas there was no among tree variation. In contrast, the activities of antioxidative CATs, which act as antagonists
to PODs, were low in young leaves and increased towards leaf maturation, reflecting an increase in the oxidative status of
source leaves. Within tree variation accounted for the most of the variation in CAT activities. The absolute PPO activities
decreased along leaf growth due to the dilution effect whereas the specific activity of PPOs, which has been shown to be defensive
against E. autumnata larvae, did not vary temporally that might reflect the importance of these enzymes in the defence of birches. Acidic PPOs
showed marked within- and among-tree variation, which may impact herbivores performance on certain genotypes and increase
larval mobility within the tree canopy. 相似文献
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