The ovules are arranged inside the ovary attached to a structure called the placenta; this arrangement is known as placentation.
Here's a breakdown of ovule arrangement and placentation:
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Ovule Attachment: Ovules, which contain the female gametophyte (embryo sac), are attached to the inner wall of the ovary. The point of attachment is the placenta.
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Placentation: Placentation refers specifically to the arrangement of ovules within the ovary. It's a crucial characteristic in plant identification and classification.
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Types of Placentation: There are several basic types of placentation:
- Marginal: Ovules are attached along one margin or suture of the ovary. This is typical of simple pistils (e.g., pea pods).
- Axile: Ovules are attached to a central axis in an ovary with two or more locules (chambers). (e.g., tomato, lemon).
- Parietal: Ovules are attached to the ovary wall or on extensions of it. The ovary is typically one-chambered. (e.g., cucumber, mustard).
- Free Central: Ovules are attached to a central column that is not connected to the ovary wall by partitions. The ovary is one-chambered. (e.g., Dianthus).
- Basal: A single ovule is located at the base of the ovary. (e.g., sunflower).
- Apical: A single ovule is located at the apex (top) of the ovary (Less Common).
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Importance of Placentation: The type of placentation can affect the number of seeds that develop and how they are dispersed. It's an important feature used to differentiate between plant species.
