Name: Bulliform Cells
Uploaded: 2019-07-19
Duration: 5 min 39 s
Description: Comprehend the anatomy of the isobilateral leaf and learn about one of its modified structures, the bulliform cells that help the plant deal with stress-indu...

Question

What is placentation? Describe various types of placentations with examples.

Accepted Answer

The ovary is the swollen basal portion of the carpel of the gynoecium in which ovules are located. The ovules remain attached to the inner wall of the ovary to a parenchymatous outgrowth called the placenta. The mode of arrangement of the ovules on the placenta is called placentation.

Different types of placentations are found in plants such as:

Marginal: The type of placentation in which the placenta develops along the fused margin (ventral suture) of the carpel is called marginal placentation. These plants possess monocarpellary gynoecium. Example: pea, bean, etc.

Axile: The type of placentation in which the placenta placed at the centre of a multilocular ovary and the ovules placed along the axis is called axile placentation. It is present in the syncarpous ovary in which carpels are fused. It is found in china rose, cotton, etc.

Parietal: In this type, the ovary is one chambered and the placentae bearing the ovules develop on the inner wall of the ovary. This type of placentation is called parietal placentation. Examples: Argemone

Basal: The placenta develops from the base of the one chambered ovary. The placenta is placed on the tip of the thalamus on the floor of the ovary. This type of placentation is called basal placentation. Examples: sunflower, marigold, etc.

Free central: The placenta develops from the central axis of one chambered ovary. In this case, the partial walls between the chambers being dissolved. Example: soapwort.

Superficial: The ovary is multicarpellary and multilocular. In this, the whole inner walls of the chambers are lined with placental tissue, so the ovules developed around. It is similar to axile placentation but the ovule bearing placentae are borne on the surface of the parietal wall. Example: water lily.

What is placentation? Describe various types of placentations with examples.

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