Effect of elevated CO2 on the stomatal distribution and leaf physiology ofAlnus glutinosa

Variation in stomatal development and physiology of mature leaves from Alnu s glutinosa plants grown under reference (current ambient, 360 mu mol mol(- 1) CO2) and double ambient (720 mu mol mol(-1) CO2) carbon dioxide (CO2) mo le fractions is assessed in terms of relative plant growth, stomatal charac ters (i.e. stomatal index and density) and leaf photosynthetic characters. This is the first study to consider the effects of elevated CO2 concentrati on on the distribution of stomata and epidermal cells across the whole leaf and to try to ascertain the cause of intraleaf variation. In general, a do ubling of the atmospheric CO2 concentration enhanced plant growth and signi ficantly increased stomatal index. However, there was no significant change in relative stomatal density. Under elevated CO2 concentration there was a significant decrease in stomatal conductance and an increase in assimilati on rate. However, no significant differences were found for the maximum rat e of carboxylation (V-emax) and the light saturated rate of electron transp ort (F-max) between the control and elevated CO2 treatment.