The effect of variation in light and nitrogen on the composition of resin in young Sitka spruce

In a previous study of growth and defence in young Sitka spruce of Alaskan or Oregon provenance,'high' and 'low' light and nitrogen treatments induced changes in quantitative defences that were broadly as predicted by resource availability models of defence. In the present study, resin extracts from leaves, stern and roots of these spruce trees were examined for changes in composition induced by the different light and nitrogen treatments. Canonical variate analysis of terpene log ratios revealed significant differences in resin composition between the roots, stems and needles. Treatments had no significant affect on resin composition of roots and stems, but both light and nitrogen treatments induced significant changes in the terpene composition of resin from needles, with evidence of variation in response between the two provenances. Induced changes in composition of quantitative defences should not be ignored in studies of environmental effects on plant resistance.