Morphological, physiological, and biochemical responses of Pistacia atlantica seedlings to elevated CO2 concentration and drought stress

Elevated atmospheric CO2 concentration and changes in precipitation patterns affect plant physiological processes and alter ecosystem functions. In combination, the interactions between these factors result in complex responses that challenge our current understanding. We aimed to investigate the effects of elevated CO2 and drought stress on the growth and physiology traits of One-year-old Pistacia atlantica seedlings. Seedlings of P. atlantica were grown at two different CO2 concentrations (ambient 380 ppm and elevated 700 ppm) and the two irrigation regimes (100% and 50% of field capacity) for one growing season. Seedlings collar diameter, height, leaf area, biomass accumulation, root length and volume, photosynthetic parameters, pigment content, and relative water content increased at elevated CO2. At the same time, the amounts of proline, electrolyte leakage, malondialdehyde, and antioxidant enzymes decreased at elevated CO2. Drought stress had negative effects on the measured growth parameters. These, however, ameliorate in the presence of elevated CO2 through enhanced photosynthesis performance and maintaining better water status, and possibly also by a reduction of oxidative stress. Increased CO2, as expected in a future climate, might thus mitigate the negative effects of drought in P. atlantica trees under natural conditions.