Describe the various types of placentations found in flowering plants.
Explanation Placentation refers to the way or arrangement of the placenta in the plant ovary. They are of different types- Marginal: It is a simple type of placentation. The placenta develops longitudinally as a ridge on the ventral suture of the ovary and ovules develop on this ridge. It forms two rows like in pea for example. Prietal: In this type of placentation, the placenta develops on the parietal wall of the ovary. The ovules can develop on the inner wall or on the peripheral part. There are two modifications of this type of placentation- The ovary is single chambered but often the development of a false septum between the two placenta divides the ovary into two. Example- Brassica campestris. The placenta in some cases project inwards towards the ovary cavity and forms an incomplete septa where the ovaries develop. Example- Poppy .Free Central: The placenta develops at the centre of the ovary and is not connected to the ovary wall in this type of placentation. In addition to that, they lack septa hence it is called free central. Example- Dianthus Basal :In this type of placentation, the placenta develops at the base of the ovary. The placenta has only one ovule attached to it. Example- Sunflower. Final Answer Placentation refers to the way or pattern or the arrangement of the placenta in the ovary. There are different types of placentation- Marginal- which is a simple type of placentation in which the placenta develops as a ridge on the ventral suture of the ovary.The ovules develop as rows on either side. Parietal- In this the placenta develops either on the inner wall or peripheral part of the parietal part of the ovary. Free Central- this type of placentation has no septa and the placenta develops at the centre of the ovary with no connection to the wall. Basal- In this type of placentation, the placenta containing a single ovule develops at the base of the ovary.
