Question

The arrangement of ovules within the ovary is known as placentation. What does the term placenta refer to? Draw various types of placentations in the flower as seen in T.S. and V.S.

Answer 1

Placenta

Placenta refers to the tissue present on the inner wall of the ovary through which ovules are attached with the ovary.

Types of placentation

The different types of placentation found in flowers are as follows:

• Marginal: The placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows. Example: Pea.
• Axile: When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentation is said to be axile. Example: China rose, tomato and lemon.
• Parietal: In parietal placentation, the ovules develop on the inner wall of the ovary or on the peripheral part. Ovary is one-chambered but it becomes two-chambered due to the formation of the false septum. Example: Mustard.
• Free central: When the ovules are borne on the central axis and septa are absent, the placentation is called free central. Example: Dianthus and Primrose.
• Basal: The placenta develops at the base of the ovary and a single ovule is attached to it. Example: Sunflower, marigold.