Placentation

Placentation is the manner in which placentae are distributed in the ovary. Placenta is the point of attachment of ovules (or future seed) in the ovary.

Types of Placentation

(i) Marginal - The ovary is monocarpellary and one chambered and ovules are arranged along the fused margins of the single carpel. Example: pea, gram

(ii) Axile - Ovary is polycarpellary syncarpous, having many chambers and ovules present on the placenta develop from the central axis formed by the fusion of the margins of two or more carpels. Example: China rose, tomato, bhindi

(iii) Parietal - Ovary is polycarpellary and syncarpous, having one chamber and ovules are attached on its inner wall where margins of adjoining carpels meet. Example: mustard, cucumber

(iv) Basal - Ovary is bi-or polycarpellary, syncarpous, having one chamber and placenta develops at the base of ovary and bears a single ovule. Example: sunflower

(v) Free central - Ovary is syncarpous and polycarpellary but unilocular as septae are absent. In the central part of the ovary the placenta bears many groups of ovules. Example: Dianthus, Primula

(vi) Superficial - Ovary is polycarpellary syncarpous and multilocular in which Plants and animals entire inner walls of chambers are lined with placental tissue so that ovules develop all around. Example: water lily (Nymphaea)