Fig. 1. Changes in specific leaf mass (SLM) referred to dry weight (DW), leaf area and soluble protein during sunflower primary leaf development. Plants were grown under
different atmospheric CO2 concentrations: 400 -
L L−1 (closed circles) and 800 -
L L−1 (open circles). Data are means ± SD of duplicate determinations from three separate
experiments. Asterisks indicate statistically significant differences among the CO2 treatments at the indicated times according to Student’s t-test (P < 0.05).