STOMATAL PATTERNS IN EMBRYOPHYTES: THEIR EVOLUTION, ONTOGENY AND INTERPRETATION

Abstract

SummaryThe history of study and nomenclature of stomatal concepts has not yet led to full elucidation of cell pattern significance for higher plants. In this paper, a new ontogenetic system of classification is introduced that makes primary subdivision on the basis of the mode of division of the guard mother cell (GMC) with respect to the wall which cuts it from the meristemoid: diameristic, at right angles; parameristic, parallel to; and anomomeristic, without special orientation to the preceding wall. These are further subdivided on the basis of ontogeny and number of the surrounding cells. The biology of stomata is discussed as it relates to cell patterning, and fundamental ties are pointed out between stomatal configurations and epidermal ontogeny, especially with regard to whether development is rectate, proceeding in a wave from an intercalary or marginal meristem, or diffuse, proceeding with continued meristematic activity within the expanding tissue over a long period of time. The concept of perigenous stomata, those in which protodermal cells act directly as GMC's without prior division, is refuted. The primitive stoma of land plant sporophytes is interpreted to be the simplest type of diameristic, mesoperigenous stoma, in which a protodermal meristemoid divides transversely, cutting off a distal GMC which then divides longitudinally to produce the guard cells. This stoma is suggested as the progenitor type for the Angiospermae, and is the primitive type for at least the Monocotyledonae.