Question

What are the different types of placentation in flowers?

Answer 1

The different types of placentation in flowers are:

Type	Found in	Description	Examples
1.  Marginal	Monocarpellary ovary	Ovary unilocular. Ovules arranged along margin of unilocular ovary	Pea, Clitoria, Groundnut
2. Parietal	Bi or multicarpellary ovary but unilocular	Ovules arranged along periphery. Number of placentae corresponds to the number of carpels	Cucurbita, Argemone
3. Axile	Bi or multicarpellary and multilocular ovary	Ovules arranged along the central axis of placenta. Number of chambers correspond to the number of carpels	Lemon, Tomato, Hibiscus, Cotton
4. Free central	Multicarpellary, syncarpous ovary	Ovules borne along the central axis which is not connected with the ovary wall by septum.	Carnations
5. Basal	Monocarpellary but unilocular	Single ovule attached at the base	Sunflower, Tridax
6. Superficial	Monocarpellary or Polycarpellary ovary which are syncarpous	Ovules develop on the whole inner surface of the ovary including septa	Nymphea

 

Answer 2

Placentation is the arrangement of ovules on the placenta inside the ovary. Based on the number of locules in the ovary and the position of the ovules there are different types of placentation. There are eight different types of placentation observed in the angiosperm flowers.

They are; i. Marginal, ii. Parietal, iii. Axile, iv. Free central, v. Basal, vi. Superficial, vii. Pendulous, viii. Lamellar.

1. Marginal: Presence of monocarpellary unilocular gynoecium.  Single row of ovules along the ventral sutures of the carpel. This type of placentation is common in the members of Leguminosae.
2. Parietal: Presence of multicarpellary syncarpous and unilocular gynoecium. The ovules are borne on the inner surface of the ovary wall. Parietal placentation is present in Cruciferae, Capparidaceae.
3. Axile: Presence of multicarpellary, syncarpous and multilocular gynoecium. The placenta is present on the fused margins of the same carpel. The ovules are attached along the central axis. Axile placentation is observed in the Malvaceae, Rubiaceae, Solanaceae etc.
4. Free central: Presence of multicarpellary, syncarpous and unilocular gynoecium. The ovules are borne on a central column arising from the base. Example as in Portulacaceae, Primulaceae.
5. Basal: Presence of monocarpellary and unilocular gynoecium. The placentum arise from the basal region from which the ovules also arise. Example as in Asteraceae.
6. Superficial: Presence of multicapellary, syncarpous and multilocular gynoecium. The ovules are borne all over the inner surface of the ovary. Superficial placentation is also known as the laminar placentation. This type of placentation is observed in Nymphaeceae and Butomaceae.
7. Pendulous: The placenta present at the top of the ovary and ovule hanging down. The pendulous placentation is found in Combretaceae.
8. Lamellar: The placenta enlarges considerably and extands towards the centre.This type of placentation is observed in Papaver of family Papaveraceae.