Understanding Placentation Types

Placentation refers to the arrangement of ovules within the ovary of a flower. Different types of placentation exist based on how the ovules are attached or distributed. Let's explore the options provided in relation to the question.

Parietal Placentation Explained

In Parietal placentation, the ovules develop on the inner wall of the ovary or on the peripheral region. The ovary is typically unilocular (single chambered), but it can appear to be bilocular due to the formation of a false septum. This type of placentation is characteristic of plants like mustard (Brassica) and argemone. The seeds develop from these placentae which are often raised ridges on the inner surface of the ovary wall.

Comparison with Other Placentation Types

• Axile Placentation: Here, the ovary is divided into several compartments or locules. The ovules are attached to the central axis formed by the fusion of septa (partitions) dividing the ovary. Examples include Hibiscus and tomato. This differs from the description given.
• Free Central Placentation: In this type, the ovules develop from the central axis, and septa are absent, making the ovary unilocular. Examples include Dianthus and Primula. The ovules are not on the inner wall but rather in the center without partitions.
• Basal Placentation: This is characterized by a single ovule attached at the base of the ovary. The ovary is typically unilocular. Examples include sunflower and marigold. This arrangement is very different from the ovules being on the inner wall.

Conclusion on Parietal Placentation

The question specifically describes placentation where ovules are on the inner wall of the ovary or the peripheral part, citing mustard and argemone as examples. This description perfectly matches the definition and examples of Parietal placentation.