Types of Placentation

Placentation refers to the arrangement of the ovules within the ovary of a flowering plant. It plays a vital role in the development of seeds and fruits. There are several types of placentation, each with its distinct characteristics. Let's explore five different types of placentation.

1. Marginal Placentation:
In marginal placentation, the placenta is located along the margin or edge of the ovary. The ovules are attached to a single elongated placenta, forming a ridge-like structure. Examples of plants exhibiting marginal placentation include the pea family (Fabaceae) and the violet family (Violaceae).

2. Axile Placentation:
Axile placentation occurs when the placenta is located in the center of the ovary, forming several chambers or locules. The ovules are attached to the central axis, and each locule contains multiple ovules. This type of placentation is commonly found in fruits like the tomato and watermelon. It is also observed in families such as the lily family (Liliaceae) and the citrus family (Rutaceae).

3. Free Central Placentation:
In free central placentation, the ovules are attached to a central column or stalk, known as the placenta. The ovary is not divided into separate chambers, and the ovules are arranged on the placenta in a clustered manner. Examples of plants with free central placentation include the primrose family (Primulaceae) and the poppy family (Papaveraceae).

4. Basal Placentation:
Basal placentation occurs when the placenta is located at the base or bottom of the ovary. The ovules are attached to a single basal placenta. This type of placentation is common in flowers with a superior ovary, where the other floral parts (such as sepals, petals, and stamens) are attached above the ovary. Examples include the lily-of-the-valley and the orchid family (Orchidaceae).

5. Parietal Placentation:
Parietal placentation is characterized by the placenta being situated along the inner wall or periphery of the ovary. The ovules are attached to the placenta, and the ovary may have one or more chambers. Parietal placentation is observed in families such as the mustard family (Brassicaceae) and the rose family (Rosaceae).

In conclusion, placentation is a crucial aspect of flower structure and fruit development. The different types of placentation, including marginal, axile, free central, basal, and parietal, demonstrate the diversity and adaptation of flowering plants. Understanding placentation helps in the identification and classification of plant species and provides insights into their reproductive strategies.

Just refer ncert pg no . 75 for this ......