Elevated temperature and carbon dioxide affect chlorophylls and carotenoids in douglas-fir seedlings

The objective of this study was to determine whether increased temperature and CO2 concentration would decrease or increase the concentrations of foliar pigments in S-yr-old seedlings of Douglas-fir Pseudotsuga menziesii [Mirb,] France var, menziesii). Seedlings were grown for 3 yr in sunlit, controlled environment chambers under ambient conditions or with a 179 mu L L-1 elevation of CO2 and/or a 3.5 degrees C elevation of temperature. Current- and previous-year needles were extracted with methanol for determination of chlorophylls and b, total carotenoids, and UV-absorbing compounds. Interactive effects of elevated temperature and CO2 on the measured responses were not significant. Current-year needles from the elevated CO2 treatment had the lowest chlorophyll and carotenoid concentrations, whereas needles of both age classes in the elevated temperature treatment had the highest concentrations of chlorophylls; current-year needles had the highest carotenoid concentration at elevated temperature. Neither temperature nor CO2 affected the concentrations of UV-absorbing compounds or needle fresh mass significantly. Chlorophyll a was correlated with carotenoids across all treatments (r = 0.75-0.89) in both needle age classes and with chlorophyll b in most treatments.