Influence of stomatal rings on movements of guard cells

摘要

Key messageThe leaf stomata of some evergreen plants have cuticular rings. According to dynamic modeling, being the ribs of rigidity these rings are able to influence the stomatal mechanics.AbstractThe cuticular folds are typical of the leaf surface of many flowering plant species. They are often present on the stomatal complex cells. The functions of such folds are still underinvestigated. This study aims to elucidate the role of the stomatal rings in guard cell mechanics. Light, scanning, and transmission electron microscopy were used to study the stomata of the leaf epidermis in Viburnum suspensum (Caprifoliaceae), Lauro-cerasus officinalis (Rosaceae), Exbucklandia populnea (Hamamelidaceae), and Acokanthera oblongifolia (Apocynaceae), which have stomatal rings. The rings are formed by cuticular folds and can be located either immediately on guard cell walls around the outer ledges (marginal stomatal rings), or on the outer ledges themselves (rings of ledges). To elucidate the role of the rings, we have applied dynamic modeling using the finite element method. The data on the shape of the guard cells, uneven thickness of their walls, localization and the relative sizes of stomatal ledges and rings were exactly reproduced during model stomata construction. The turgor pressure was simulated by creating the load distributed on the inner surface of the guard cells. The guard cells of all studied species are located on the subsidiary or neighboring cells. The modeling has shown that the presence of the marginal rings leads to sinking of the opening stomatal pores into epidermis. The depth of the sinking depends on mechanical characteristics of marginal rings. The rings of ledges rib the outer ledges and prevent the outer ledges aperture widening when the stoma is opening.