Question

Which of these is an example for a zygomorphic flower with diadelphous stamens and marginal placentation?
A. Pea
B. Lemon
C. Brinjal
D. Cucumber
E. China rose

Answer 1

Hint: Placentation refers to how the ovules and developing seeds are fixed to the plant's ovary. Every single developing seed will fix with the ovary wall or a central structure in the ovary. A filament of plant tissue is defined as the funiculus that affixes the seed to the ovary wall. The male reproductive structure of a flower is stamens. Stamens are composed of anther and a filament. They denote androecium.

Complete step-by-step answer:
Placentation indicates the structure, kind, formation and or arrangement of placentas. The area of the ovary wall in which the ovules are connected in a flower is known as the placenta.
Marginal placentation
The placenta creates a ridge along through the ventral suture of the ovary, ovules are borne on the ridge to form two rows. A single longitudinal placenta or file of ovules is fixed to the ovary wall. The ovary is always unilocular. Example: Pea
Diadelphous stamen
Diadelphous androecium forms in two groups or bundles once the filaments of the stamens are fused. It is visible in the flowers of Dolichos. It is thought to be monadelphous if the filaments of the stamens are combined into a single group. e.g., Pea.
Zygomorphic flowers‌
Flowers that can be split into two halves from one plane are called zygomorphic flowers. Pea, Gulmohar, cassia, and beans show zygomorphic flowers.
Hence the correct answer is Pea.

Note: Placentation is the layout of ovules in the ovary of a plant. The function of placentation is to transmit respiratory gases, nutrients, and water from maternal tissue to a growing embryo, and in certain cases to eliminate waste from the embryo. Usually, stamens in a simple flower are arranged as individual units.