Effects of CO2 Enrichment on Four Poplar Clones. II. Leaf Surface Properties

The poplar clones Columbia River, Beaupre, Robusta and Raspalje have been investigated in the present (350 μmol mol−1) and double the present (700 μmol mol−1) atmospheric CO2 concentration. Cuttings were planted in pots and were grown in open-top chambers inside a glasshouse for 92 d. Stomatal density, stomatal index, length of stomatal pore and epidermal cell density were not affected by CO2 enrichment in any of the clones. Lack of differences in stomatal density or index indicate that there were no direct effects of CO2 enrichment on the initiation of the number of stomata during ontogenesis or on epidermal cell expansion at a later stage. Stomatal conductance decreased because of the effect of CO2 on stomatal opening. The average reduction in both adaxial and abaxial surface has been estimated at 41%. Beaupre showed the largest response of stomatal conductance and Columbia River the smallest.