Figure 1.

Overview of Cell Types.

The stomatal lineage begins when a meristemoid mother cell (MMC; gray shading) forms and then divides asymmetrically, producing a meristemoid and a larger sister cell. Meristemoids divide asymmetrically zero to three times and then convert into guard mother cells (GMCs). The latter divide symmetrically, producing two guard cells. Smaller, less sinuous epidermal cells (upper left) become MMCs and divide asymmetrically (i), divide symmetrically (ii), or form wavy pavement cells (iii). Cells adjacent to a stoma or precursor can initiate a new stomatal lineage (iv and v), as can cells that are not adjacent. The first division of an MMC located next to a stoma or precursor is oriented so that the resulting satellite meristemoid is placed away (bottom left). Satellite meristemoids can divide zero to three times (only one division is illustrated in the bottom row). Neighbor cells that are clonally related to the stoma (see text) are drawn with solid rather than dashed lines (top row). The three stomatal complexes shown at top right are anisocytic. Div., division; M, meristemoid; SM, satellite meristemoid.