Question

Describe the various types of placentation found in flowering plants.

Answer 1

Placentation of flowering plants is the distribution of ovule-bearing cushions or placentae inside the ovary. It is of the following types.

1. Marginal: A monocarpellary unilocular ovary bears ovules longitudinally along the ventral suture in one or two alternate rows. For example, Pea.

2. Parietal: A syncarpous, unilocular ovary bears two or more placentae longitudinally along the wall. For example, Fumaria, Viola. A false septum or replum occurs between two parietal placentae in Mustard. It makes the ovary falsely bilocular. In cucurbits, the three parietal placentae grow inwardly, meet in the centre and bend outwardly. The ovary becomes trilocular. In Poppy and Prickly Poppy, the ovule-bearing parietal placentae grow inwardly to form incomplete septa.

3. Axile: A syncarpous bilocular to multilocular ovary bears ovules on the central axile column where the septa meet. For example, Shoeflower, Petunia, Asphodelus.

4. Free Central: Polycarpellary syncarpous but unilocular, ovary bears ovules around a central column which is not connected to ovary wall, e.g., Pink.

5. Basal: Unilocular ovary bears a single ovule from the basal region. For example, Ranunculus, Sunflower.

6. Apical: Unilocular ovary bears a single ovule from the apical region. For example, Cannabis.

7. Superficial: Ovules are borne along the inner surface of ovary including the septa if present. For example, Butomus (unilocular), Nymphaea (multilocular).