Different Fagus sylvatica genotypes under high level of CO2: gene expression and ecophysiology analyses

The problems related to global changes mainly caused by human activities, are the origin of much concern for the health of the environment. Oil and carbon combustion, the use of chlorofluorocarbons, and deforestation are some of the principal factors responsible for enhanced CO2 production, as well as for air temperature increases. This scenario could determine global changes affecting precipitation patterns, nitrogen concentration in the atmosphere, UV radiation increase, and temperature range. Forest trees constitute a relevant economic and ecological resource that is under severe treat by environmental changes. The principal aim is to investigate the response to CO2 from two different F. sylvatica genotypes by gene expression and ecophysiology analyses. Scions of Fagus sylvatica (Montieri (GR), Italy) and F. sylvatica "purpurea tree" (Grosshansdorf, Germany) were grafted on F. sylvatica rootstocks. Plants were grown under controlled conditions in climate chambers. Air temperature was 25°C during light period and 20°C at night, and humidity 60%. Fluorescent lamps (18 36W) provided a photosynthetic active photon flux density (PPFD) of 250 ?mol m-2 s-1 at plant top level. CO2 concentrations were about 450 ppm (ambient) and 1000 ppm (high) for control and high CO2 chamber, respectively. A PAM fluorescence system (PAM-2000, Heinz Walz GmbH, Effeltrich, Germany) with a 6 mm diameter standard fibre optic was used for the measurements of the in vivo photosynthesis. Light response curves were recorded up to a light intensity of 420 ?mol m-2 s-1. At each step the leaf was illumined for 3 minutes. Under ambient CO2 concentrations, electron transport rate (ETR) was higher in the Italian compared to the German genotype. After 4 days at high CO2 level, the ETR increased compared to plants growing in the control chamber. Photosynthesis of Italian genotype adapted to 1000 ppm of CO2 decreased immediately after been exposed for 2 hours to 450 ppm CO2. No down-regulation of photosynthesis could be observed in leaves at 1000 ppm CO2 level. Microarray analyses are in course and preliminary results will be discussed.