Figure 1.

Diagram representing the influence of changes in stomatal anatomy (density and size; left panels, stomatal clustering; lower panels) on stomatal conductance (g_s, arrows) and the rate of g_s response (red lines). The impact of anatomical traits on carbon gain (A, dashed lines), the limitation of A by g_s (green area) and water use efficiency (W_i) are illustrated. The influence of stomatal density and size (vertical arrow) and stomatal clustering (horizontal arrow) on the rate of g_s response and the maximum or operational value of g_s is highlighted.