Types of Placentation in Ovary — NEET Biology
✅ Asked in NEET 2023Placentation: The arrangement of ovules within the ovary is known as placentation. The placentation are of different types namely, marginal, axile, parietal, basal, central and free central. In marginal placentation the placenta forms a ridge along the ventral suture 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 peripheral part. 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 central axis and septa are absent, as in Dianthus and Primrose the placentation is called free central. In basal placentation, the placenta develops at the base of ovary and a single ovule is attached to it, as in sunflower, marigold.
Axile placentation is the most commonly tested type where ovules attach to a central axis in a multi-chambered ovary (seen in tomato, lemon, china rose). Students often confuse axile with free central placentation—axile has septa dividing chambers while free central lacks them completely. Another trap: mixing up parietal (ovules on ovary wall, one chamber) with axile (ovules on central axis, multiple chambers). Key to remember: 'axile' = axis in center, 'multi' = many chambers. The NTA repeatedly tests identification through examples and distinguishing between marginal (pea), basal (sunflower), and axile types using flower characteristics.
This paragraph was tested 4 times in NEET.
Axile placentation is observed in:
Match the placental types (Column I) with their examples (Column II). Choose the correct answer from the following options: Column I (A) Basal (B) Axile (C) Parietal (D) Free central Column II (i) Mustard (ii) China rose (iii) Dianthus (iv) Sunflower
Match the placental types (Column-I) with examples (Column-II): A. Basal B. Axile C. Parietal D. Free central (i) Mustard (ii) China rose (iii) Dianthus (iv) Sunflower
Placentation, in which ovules develop on the inner wall of the ovary or in peripheral part, is:
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