Describe the various types of placentations found in flowering plants
The arrangement of ovules within the ovary is known as placentation. The placentation of different types namely, marginal, axile, parietal, basal, central, and free central. In marginal placentation, the placenta forms a ridge along with the central structure of the ovary and the ovules are borne on this ridge forming two rows, as in pea. When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentation is said to be axile, as in china-rose, tomato, and lemon. In parietal placentation, the ovules develop on the inner wall of the ovary or on the peripheral part. The ovary is one-chambered but it becomes two-chambered due to the formation of the false septum e.g. mustard and Argemone. When the ovules are borne on the central axis and septa are absent, as in Dianthus and Primrose; this type of placentation is called free central. In basal placentation, the placenta develops at the base of the ovary and a single ovule is attached to it, as in sunflower, marigold.
