The arrangements of ovules within the ov | Class 11 Biology Chapter Morphology of Flowering Plants, Morphology of Flowering Plants NCERT Solutions

The attachment of ovules within the ovary is known as Placentation. The placenta refers to a flattened, cushion like tissue on which one or more ovules are attached to the inner-surface of ovary wall. It provides nutrition to the embryo. Various types of placentation in the flower are:

1. Parietal: Occurs in a bi- or multicarpellary but unilocular ovary. Placenta appears as internal ridges on the ovary wall.
2. Marginal: Occurs in a monocarpellary, unilocular ovary. Placenta develops and ovules are borne along the junction of the two margins of the carpel.
3. Axile: Occurs in a bi- or multicarpellary and multilocular ovary. Placentae are formed in the center of the ovary by carpel’s margins inward folding by fusing together in the center.  
4. Free- central: Occurs in multicarpellary but unilocular ovary. Placenta develops in the center of ovary as an upgrowth from ovary base which bears ovules. It may also formed by breaking down of the septa from the initial axile placentation, like in caryophyllaceae.    
5. Basal: Occurs in a bi- or multicarpellary but unilocular ovary. The ovules are few or reduced to one and borne at the base of the ovary.
6. Superficial: Occurs in a multicarpellary and multilocular ovary. Ovules are borne on placentae which develops all around the inner surface of the partition wall.