Question

In unilocular ovary with a single ovule, the placentation is:
(a) Axile
(b) Marginal
(c) Basal
(d) Free Central

Answer 1

Hint: The mode of arrangement or distribution of placenta and ovules within the ovary is called placentation. The placenta is parenchymatous tissue which acts as an attachment site for the ovules in the ovary.

Complete answer:
An ovary can have one or more than one placenta. In Basal placentation, the ovary is unilocular. It bears a single placenta positioned at the base of the ovary and a single ovule is attached to it. The pistil or carpel may be monocarpellary or syncarpous. E.g. Ranunculus, Sunflower, Marigold etc.
Other types of placentation may be as follows:
Marginal Placentation: Two rows of longitudinally placed ovules are seen attached to the ventral sutures or the fusion of the two margins of ovary’s walls. Ventral sutures are the first line of dehiscence for the ripening of fruits. This type of placentation is found in monocarpellary pistils. E.g. Leguminous plants such as pea, Cassia.
Parietal Placentation: Due to the syncarpous or compound pistil, two or more longitudinal placenta develops along the walls of the ovary. The number of placenta is synonymous to the number of carpels fused. Like in Funaria, two carpels fuse, three in Viola and four in Capparis.
Axile Placentation: Placentation occurs in the middle of the ovary where the septa of partitioned ovaries meet. It occurs in the syncarpous ovary. E.g. Petunia, Tomato.
Free central Placentation: The pistil is polycarpellary and syncarpous but the ovary is unilocular. The ovules are borne around a central column which is not connected with the ovary wall by any septum.
E.g. Primrose, Dianthus.
So, the correct answer is ‘Basal.’

Note: Pistil/Carpel or female part of the plant is composed of stigma, style and ovary. If gynoecium has only one ovary, it is called monocarpellary, if two then bicarpellary and tricarpellary then three ovaries are present. These carpels may be fused or free. If fused, then they are termed as syncarpous and if free, then they are termed as apocarpous. The ovary may contain one locule (compartment) as in a unilocular ovary or two as in bilocular and so on.