THE EFFECT OF ELEVATED CARBON-DIOXIDE AND FERTILIZATION ON PRIMARY AND SECONDARY METABOLITES IN BIRCH, BETULA-PENDULA (ROTH)

Seedlings of European white birch (Betula pendula Roth) were grown in growth chambers for one growth season under four carbon dioxide regime s (350, 700, 1050 and 1400 pm) and at three fertilization levels (0, 1 00 and 500 kg ha(-1) monthly). The soluble carbohydrates and secondary phenolics in the leaves and stems were analysed. It was found that fe rtilizer addition reduced the amounts of glucose and fructose while su crose remained almost unaffected. The sugar content of leaves increase d at 700 ppm and 1050 ppm of CO2 and decreased at the highest CO2 conc entration (1400 ppm). The amounts of proanthocyanidins and flavonoids in leaves decreased with fertilization addition and increased with CO2 enrichment. The production of simple phenolic glucosides varied accor ding to the fertilization and CO2 treatments. The triterpenoid content of stems seemed to increase with fertilization and CO2 addition. Our results indicate that the production of phytochemicals in the birch se edlings is very sensitive to both fertilization and CO2 addition, whic h is in agreement with earlier studies, and thus provide some support for the hypothesis of carbon allocation to plant defence when there is an excess of carbon and nutrient. The considerable variation in the p roduction of secondary components may indicate that the synthesis of t hese defensive metabolites can be regulated by a plant to certain exte nt, depending on the ability of the plant to acclimate to changes in t he physical environment.