Figure 2.

Stomatal apertures of three seed plants A. thaliana, S. japonica, and G. biloba, the fern M. struthiopteris and lycophyte S. moellendorffii in response to ABA, Ca²⁺, and D-sorbitol solution. A, ABA and (C) CaCl₂-induced stomatal closure in the seed plants, but did not in the fern and lycophyte. B, Images of epidermal peels showing ABA-induced stomatal closure in the three seed plants, but not in the fern and lycophyte (bar = 10 µm). D, Hypertonic D-sorbitol solution (800 mM) induced stomatal closure in the three seed plants, and the fern and lycophyte. Forty stomatal pores were measured in each separate replicated experiment in each individual plant (three different plants per treatment). Data are means ± se (total stomatal number per treatment = 120, n = 3). Statistically significant differences between treatments and the control within each species are denoted with asterisks (two-way ANOVA, P < 0.05)