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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

 

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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.
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