Genotypic differences in growth and stomatal morphology of Southern Beech, , exposed to depleted CO concentrations

Nothofagus cunninghamii (Hook.) Oerst. clones of four different genotypes from Mt Field National Park, Tasmania were grown at both current (~370 mol mol –1 ) and depleted (~170 mol mol –1 ) CO 2 . Growth was significantly less in the lower [CO 2 ] treatment in all genotypes. The amount of growth reduction caused by low [CO 2 ] depended strongly upon genotype and varied from less than 30% to greater than 75% reduction of whole plant biomass when compared to growth at current [CO 2 ]. Specific leaf area was significantly greater in all plants grown in reduced [CO 2 ], whereas individual leaf area was not significantly affected by [CO 2 ]. The direction and magnitude of the response of stomatal index, stomatal density and epidermal cell density to [CO 2 ] was strongly dependent upon genotype. [CO 2 ] had a significant effect on the length of the stomatal pore, but the magnitude of the effect (~3%) was trivial compared to changes in stomatal density (up to 20%). There was a significant (P < 0.01) and positive relationship between the response of stomatal density and growth response of a genotype. Therefore, we propose that the response of stomatal density to [CO 2 ] controls the relative growth response of N. cunninghamii and that this response is highly dependent upon genotype. Australian Journal of Plant Physiology 27(4) 281 - 287 Full text doi:10.1071/PP99195 © CSIRO 2000