Effects of elevated CO2 and decreased water availability on holm-oak seedlings in controlled environment chambers

In Mediterranean ecosystems, water is an important limiting factor forplant growth. In addition to the increase in atmospheric CO2, somemodels predict increased drought in Mediterranean areas as a consequenceof global change. Thus, to determine how increased atmospheric CO2interacts with increased water stress and affects Mediterranean plantgrowth is an important achievement. The present study analyses how helmoak (Quercus ilex L.) seedlings are affected by both elevated CO2 andincreased water stress. The CO2 concentrations were supplied incontrolled environment chambers (350 and 500 ppm CO2), and water stresswas performed according to a Mediterranean pattern (PotentialEvapotranspiration to Rainfall ratio). The increased water stress wasattained by watering half of the Mediterranean reference pattern.Results show that the positive effects of elevated CO2 on photosynthesisand growth are counteracted by increased water stress.