Interactive Effects of Elevated [CO₂] and Soil Water Stress on Leaf Morphological and Anatomical Characteristic of Paper Birch Populations

Abstract

The leaf morphological and stomatal characteristics of four paper birch ( Betula papyrifera Marsh) populations, grown at four treatment conditions of carbon dioxide [CO 2 ] and soil water levels were investigated to determine whether future increases in atmospheric [CO 2 ] and water deficit affect ed the leaf characteristics. The populations from Cussion Lake, Little Oliver, Skimikin and Wayerton were grown for 12 weeks under ambient (360 ppm) and elevated (720 ppm) [CO 2 ] at both high and low water levels. The populations significantly differed in leaf area and stomatal characteristics due to the interaction effects of [CO 2 ], water levels and population differences. Most leaf morphological characteristics and stomatal density varied due to the effects of [CO 2 ] and/or populations, but not due to the effect of water levels. Although elevated [CO 2 ] alone barely affected stomatal area of the birch populations, simultaneous elevated [CO 2 ] at both water levels had stimulated stomatal characteristics within and among the populations. Overall, elevated [CO 2 ] reduced leaf area and increased stomatal density; and low water level resulted in smaller stomatal area, pore area and guard cell width. However, the populations responded differently to an increase in [CO 2 ] and water levels. All populations showed plastic responses with respect to [CO 2 ] and water levels either by decreasing stomatal area under low water level or by increasing stomatal density under elevated [CO 2 ]. Hence, integration between and within leaf characteristics had helped paper birch populations maintain balance between [CO 2 ] gain and water loss.