Résumé
One-year-old seedlings of Quercus ilex, a Mediterranean evergreen oak, were grown in ambient (350 mu l/l) and elevated (700 mu l/l) CO sub(2) concentrations. After the end of the growing season, leaf emissions of monoterpenes (defensive compounds important in plantparasite interactions), growth, gas exchange, leaf structure, and leaf chemical composition were measured. On average, seedlings grown under elevated CO sub(2) levels had higher monoterpene emission rates, greater foliage biomass, thicker leaves, higher leaf concentrations of cellulose and lignin, and lower leaf concentrations of nitrogen and minerals than plants grown in ambient CO sub(2) concentrations. Short-term changes in assay CO sub(2) concentrations did not significantly influence monoterpene emissions but rapidly affected photosynthetic rates. However, no long-term acclimation of photosynthesis to growth in elevated CO sub(2) concentrations was observed. All seedlings showed a strong reduction in monoterpene emission during the winter independently of CO sub(2) treatment.