Placentation – Definition & Detailed Explanation – Botanical Glossary

I. What is Placentation?

Placentation is the arrangement of ovules within the ovary of a flower. It refers to how the ovules are attached to the ovary wall and how they are positioned in relation to each other. The ovules are the structures within the ovary that develop into seeds after fertilization. The way in which ovules are arranged in the ovary can have implications for seed development and dispersal.

II. What are the Types of Placentation?

There are four main types of placentation: axile, free central, parietal, and basal. Each type is characterized by the way in which the ovules are attached to the ovary wall and how they are positioned within the ovary.

III. What is Axile Placentation?

Axile placentation is characterized by ovules that are attached to the central axis of the ovary. The ovules are arranged in a single row along the central axis, with the placenta (the tissue that nourishes the developing ovules) located in the center of the ovary. This type of placentation is common in plants with compound ovaries, such as tomatoes and peppers.

IV. What is Free Central Placentation?

Free central placentation is characterized by ovules that are attached to a central column within the ovary. The ovules are not attached to the ovary wall, but instead are attached to a central placenta that is suspended in the center of the ovary. This type of placentation is common in plants with simple ovaries, such as lilies and orchids.

V. What is Parietal Placentation?

Parietal placentation is characterized by ovules that are attached to the inner wall of the ovary. The ovules are arranged in a single row along the inner wall of the ovary, with the placenta located on the ovary wall itself. This type of placentation is common in plants with compound ovaries, such as peas and beans.

VI. What is Basal Placentation?

Basal placentation is characterized by ovules that are attached to the base of the ovary. The ovules are attached to a single point at the base of the ovary, with the placenta located at the bottom of the ovary. This type of placentation is common in plants with simple ovaries, such as primroses and poppies.

In conclusion, placentation plays a crucial role in the development and dispersal of seeds in plants. The different types of placentation, including axile, free central, parietal, and basal, each have unique characteristics that influence how ovules are arranged within the ovary. Understanding the different types of placentation can provide valuable insights into the reproductive biology of plants and how they have evolved to ensure successful seed production.