The modelling showed that outer ledges prevent wide opening of the stomatal pore and its lifting above leaf epidermis. This stomatal mechanics is combined with xeromorphic features of leaf epidermis.

Methods of light, scanning, and transmission electron microscopy were used to study the stomata of the leaf epidermis in evergreen Acokanthera oblongifolia (Apocynaceae), A. oppositifolia (Apocynaceae), Carissa spectabilis (Apocynaceae), Exbucklandia populnea (Hamamelidaceae), and Trochodendron aralioides (Trochodendraceae). The stomata of their leaf epidermis are located on subsidiary cells, have large outer ledges, and lack inner ledges. To elucidate the role of the ledges, we applied dynamic modelling using the finite-element method. The application of dynamic modelling has shown that outer ledges prevent wide opening of the stomatal pore and their rising above the surface of leaf epidermis. The results of the modelling are supported by the observed deformations in the guard cells of the real stomata. This stomatal mechanics is combined with such stomatal xeromorphic features as thick cuticle, stomatal cavities, and waxy plugs (in A. oblongifolia). All studied species show similar leaf anatomy. It has much in common with the leaf anatomy of species connected in their origin with subhumid Tertiary laurophyllous forests.