Figure 7.

Unlike seed plants, the stomata of A. filix-femina in live and intact leaves do not respond to exogenous ABA application. A to C, Mean stomatal aperture (n = 5 ± se) in continuously monitored stomata from a live, intact, photosynthesizing leaf of (A) the angiosperm R. rhabarbarum, (B) the wild-type form, and (C) the Frizelliae form of A. filix-femina. Stomata were continuously monitored for 30 min before and after an application of exogenous, aqueous 10⁻⁴ M ABA (marked by a vertical dashed line and denoted by solid circles) or a control solution of water (denoted by open circles) directly to the stomata on the surface of the leaf. In the two forms of A. filix-femina, stomata were also monitored in a leaf that was excised in air (triangle symbols; the time of excision is also marked by the vertical dashed line). D to H, Representative images of a monitored open stomata are shown immediately before the application of exogenous ABA and 30 min after the application, in (D) R. rhabarbarum and the (E) wild-type and (F) Frizelliae forms of A. filix-femina. Representative image of a monitored stomata immediately before and 30 min after leaf excision in air is also shown for the (G) wild-type and (H) Frizelliae forms of A. filix-femina. Scale bars = 25 µm.