Structure of the stomatal complex of the monocot Flagellaria indica

The structure of the mature stomatal complex of Flagellaria indica L. was studied since the Flagellariaceae is reported to be one of a handful of nongrass families with a grass‐type stoma, and since relatively little is known about stomatal ultrastructure in monocots other than grasses. Both the grass guard cell and its nucleus are dumbbell‐shaped, and the walls that separate adjacent grass guard cells are perforated. Electron and fluorescence microscopy reveal that the Flagellaria guard cell lacks these features. Instead, the Flagellaria guard cell is neither dumbbellnor kidney‐shaped, its nucleus is roughly kidney‐shaped, and the end walls are thickened and imperforate. Additional structural features of the stomatal apparatus of Flagellaria include: 1) the subsidiary cells have a protuberance that underlies the middle of the guard cell and that forms an additional and innermost aperture of the pore; 2) guard and subsidiary cell walls are thickened differentially and are layered; and 3) organelles in both cell types appear to be confined to specific domains. Although Flagellaria is closely related to grasses, it does not have a grass or dumbbell‐shaped type of stomate. This suggests that the grass type of stomate may be less widespread than reported.