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In the diatom family Chaetocerotaceae, "seta" refers to the hairlike outgrowths of the valve, i.e. of the face of the cells. [12] These setae have a different structure than the valve. Such setae may prevent rapid sinking and also protect the cells from grazing.
The seta measures 1–4 cm in height [7] and is composed of hydroids (water conducting cells), leptoids (conducting cells of sugar and other nutrients), stereids (thick walled cells that provide structural support) and parenchyma cells. Once the seta has elongated, a sporangium develops at the end of the seta.
In hornworts, the meristem starts at the base where the foot ends, and the division of cells pushes the sporophyte body upwards. In mosses, the meristem is located between the capsule and the top of the stalk (seta), and produces cells downward, elongating the stalk and elevating the capsule.
Dicranochaete consists of single cells or a few cells clustered together, attached to a substrate. Cells are hemispherical or ellipsoidal in side view. The apical portion of the cells are covered by a hood-like structure, which may be spiny, [4] and has one or more bristles, [2] also termed setae. The seta is hollow and dichotomously branched. [4]
While the foot remains anchored within the parent plant, the capsule is forced out by the seta and is extended away from the plant and into the air. Within the capsule, cells divide to produce both elater cells and spore-producing cells. The elaters are spring-like, and will push open the wall of the capsule to scatter themselves when the ...
Cell types. by origin; This is a list of cells in humans derived from the three embryonic germ layers – ectoderm, mesoderm, and endoderm. Cells derived from ectoderm
Chloroplasts (green discs) and accumulated starch granules in cells of Bryum capillare. Botanically, mosses are non-vascular plants in the land plant division Bryophyta. They are usually small (a few centimeters tall) herbaceous (non-woody) plants that absorb water and nutrients mainly through their leaves and harvest carbon dioxide and sunlight to create food by photosynthesis.
Fig A: Part of a chain showing constrictions (arrows) between mantle and girdle, and V-shaped protrusion (arrowhead) located centrally on the terminal valve. B: Dividing chain showing seta divergence. C: Structure of terminal seta. D: Chain in girdle view showing cells and apertures.