Question

How many plants in the given list have marginal placentation?
Mustard, Gram, Tulip, Asparagus, Arhar, Sunhemp, Chilli, Colchicine, Onion, Moong, Tobacco, Lupin.
A. Four
B. Five
C. Six
D. Three

Answer 1

Hint: Marginal placentation is found in plants having unilocular ovary (single chambered ovary) and ovules are arranged in a row on the ventral suture of the ovary as like Pea plants. Plants of family Leguminosae or Fabaceae show marginal placentation.

Complete answer:
The mode of arrangement of placentae or ovule within ovary is known as placentation. The ovules (which later become seeds) are connected to the walls of the ovary via the funiculi, the part of the plant equivalent to the umbilical cord. The area where the funiculus attaches to the plant is called placenta. After fertilization, the placenta of the ovule becomes the stalk of the seeds.
Types of placentation in plants area as follows:-
-Marginal placentation
-Parietal placentation
-Axile placentation
-Basal placentation
-Free central placentation

Marginal placentation is a type of placentation in which the placenta forms a ridge or margin along the ventral suture of the ovary. The ovary is simply unilocular. Ovules are borne on this ridge forming two separate rows. Marginal placentation is the characteristic property of family Leguminosae or Fabaceae.
Among the options given in the question, the plants having marginal placentation are Gram, Arhar, Sunhemp, Moong and Lupin.
Plants such as Mustard have parietal placentation. In parietal type of placentation, the ovules develop in the inner wall of the ovary or the peripheral part. Ovary is one chambered but becomes two chambered due to the formation of a false septum. It is the characteristic property of family Brassicaceae or Cruciferae.
Tulip, Asparagus, Chilli, Colchicine, Onion and Tobacco have axile placentation. In axile placentation, the placenta is axile. Ovary is multilocular and ovules are attached along the central axis of it. It is the characteristic property of family Solanaceae and Liliaceae.

Hence, the correct answer is option (B).

Note: In animals, placentation is mainly responsible for the establishment of a physical contact between the fetus and the mother inside the mother's body. It transfers the nutrients and hormones, as well as the removal of the waste products from the fetus. In the same way, placentation in plants establishes the contact between ovule and ovary. In plants, placenta performs functions like it provides connection with the ovary wall and also provides nutrition to the developing seed.