Question

Define placentation.

Answer 1

Placentation is defined as the arrangement of the placenta or placentae in the ovary of a flower.

Six type of placentation were observed in plants. They are

1. Marginal- The ovules develop in rows near the margin on the placenta e.g., Leguminosae.

2. Parietal - The placenta is formed by the swelling up of cohering margins, and on the latter develop the ovules in rows. e.g., Papaveraceae.

3. Axile - the placentae develop from the central axis which corresponds to the confluent margins of carpels. e.g., Solanaceae, Malvaceae.

4. Free-central - the placenta develops in the centre of the ovary as a prolongation of the floral axis and the ovules are attached on this axis. e.g., Primulaceae.

5. Superficial - the ovules develop over the entire inner surface of the carpels. e.g., Nymphaea

6. Basal - The placenta develops directly on the thalamus and bears a single ovule at the base of the unilocular ovary, e.g., Compositae.