Leaf structure and chemical composition as affected by elevated CO2: genotypic responses of two perennial grasses



Genotypic variability was studied in two Mediterranean grass species, Bromus erectus and Dactylis glomerata, with regard to the response to CO2 of leaf total non-structural carbohydrate concentration ([TNC]lf), specific leaf area (SLA), and leaf carbon and nitrogen concentrations ([C]lf and [N]lf, respectively). Fourteen genotypes of each species were grown together on intact soil monoliths at ambient and elevated CO2 concentrations (350 and 700 μmol mol−1, respectively). In both species, the most consistent effect of elevated CO2 was an increase in [TNC]lf and a decrease in leaf nitrogen concentration when expressed either as total dry mass [Nm]lf, structural dry mass [Nmst]lf or leaf area [Na]lf. The SLA decreased only in D. glomerata, due to an accumulation of total non-structural carbohydrates and to an increase in leaf density. No genotypic variability was found for any variable in B. erectus, suggesting that genotypes responded in a similar way to elevated CO2. In D. glomerata, a genotypic variability was found only for [Cst], [Nm]lf, [Nmst]lf and [Na]lf. Since [Nm]lf is related to plant growth and is a strong determinant of plant–herbivore interactions, our results suggest evolutionary consequences of elevated CO2 through competitive interactions or herbivory.