||"The response of stomatal pore length to signalling is complex. Pore length increases significantly (ANOVA: F=51.9, df = 3, 32, P< 0.001) when the mature leaves are shaded (experiment one, Fig. 3). Stomatal pore size doesn’t change (ANOVA: F=2.3, df = 3, 16, P> 0.05) when the developing leaves are held at low irradiance (Fig. 4). Within both experiments stomatal pore aperture remained constant between treatment and control groups." Extracted by eye from Figure 3, high light condition for control. Adaxial surface is the side of the leaf facing the stem. Upward, sun-facing surface in tobacco.