Figure 2.

Promotion of stomatal closing in adaxial (Ad) and abaxial (Ab) epidermes by ABA and Ca²⁺. Broad bean leaves were removed from plants in the light, and the epidermal tissues were peeled and kept in the light (0.160 mmol m⁻² s⁻¹) in bathing medium for 1 h before experiments. Stomatal apertures were measured under a light microscope after the epidermes were treated for 2 h in the dark. Either Ca²⁺ or ABA was added to the bathing medium at the concentrations indicated. The experiment was repeated three times. Data are expressed as means ± se (n = 60). The results for each Ca²⁺ or ABA treatment were compared with the control, and the statistical analysis (t test) was conducted at the P ≤ 0.05 (*) or the P ≤ 0.01 (**) level.