Size of stomata and palisade parenchyma on cotyledon adaxial side in someBrassica oleracea L. varieties
Cotyledons of 15 day-old seedlings of fiveBrassica oleracea L. varieties were surveyed to identify salient anatomical features. Both palisade parenchyma cells present in the first subepidermal layer and stomata were found to differ in size.
Development of Stomata in Some Cruciferae
Epidermal structure and ontogeny of stomata are described for ten species or varieties of Cruciferae. The mature stomata are typically anisocytic. Their development is of the mesogenous trilabrate type. The spiral sequence of divisions in the meristemoid may be clockwise or anticlockwise. Very often the neighbouring cells divide and form successive generations of stomata which become arranged in groups. Some theoretical implications of the study are also discussed.
Developmental studies of cell differentiation in the epidermis of monocotyledons: I. Allium, rhoeo, and commelina
Abstract Various characteristics make the epidermis of certain monocotyledonous plants, particularly the cereal grasses, favorable for studies of certain phases of developmental morphology and genetics. In the Commelinaceae, Araceae, Gramineae, and other families, development of the stomatal complex involves the following epigenetic sequence of events. In certain localized rows or areas, the cytoplasm of the protodermal cells becomes polarized, so that it is denser and contains more inclusions at the distal end of the cell. The nucleus then divides by a mitotic figure oriented across the cytoplasmic gradient. The chromosomes of this figure are similar at the two poles until early telophase, when the proximal nucleus becomes larger and more weakly staining than the distal one, both with the Feulgen technique and with acetocarmine. The distal nucleus eventually divides to form the two guard cells, but before doing so it induces division of two or more of the surrounding epidermal cells. Since in these cells there is also a cytoplasmic gradient, with a denser cytoplasm adjacent to the guard mother cell, these induced divisions are asymmetrical, with the nucleus in the center of the epidermal cell becoming larger and more weakly staining than that near the guard mother cell. In this way, subsidiary cells are formed. In the Commelinaceae, the subsidiary cells lateral to the guard mother cell are always formed before those proximal and distal to it, and a particular epidermal cell adjoining a guard mother cell always contributes a lateral subsidiary before a proximal or distal one. In Allium and other Liliaceae differentiation of the guard mother cell and guard cells is similar, but no subsidiary cells are formed. Some possible clues to the explanation of this sequence are offered, and pertinent experiments are suggested.