Flower is a modified shoot meant for reproduction. It arises as a bud in the axil of a specialized leaf called bract.
A flower consists of a short stalk or pedicel which is swollen and convex at the upper end known as thalamus. On the thalamus are inserted floral leaves in four whorls:
It is the outermost and lowermost whorl of green leaves called sepals. They protect the flower in the bud condition.
It is the inner whorl of coloured floral leaves called petals. Because of the varied colours, this whorl attracts insects which bring about pollination.
This is the third whorl of floral parts and is called the stamen. It serves as the male reproductive organ and contains male gametes called pollen grains.
It is the innermost whorl of floral parts called carpels and serves as the female reproductive organ which bears female gametes called ovules.
The specialized branches which bear clusters of flowers are called inflorescences. The main axis of an inflorescence bearing a group of flowers is called rachis or peduncle. Inflorescence may be of two types:
In this type, the main axis of the inflorescence (rachis) grows indefinitely giving rise to younger and younger flowers in an acropetal order. The rachis never terminates in a flower, the apex being left for further growth.
The growth of the cymose inflorescence is always checked vertically. In cymose, the apical bud is the oldest and younger flowers occur below it. Opening of flowers is basipetal (towards the base). Cymose inflorescences are less common than racemose types.
It is a closed capitulum in which receptacle becomes fleshy, hollow, and cup-shaped and opens at the top by a narrow opening, e.g., Ficus (Fig) and Banyan.
It consists of a cup-shaped involucre formed by the fusion of bracts. Inside involucre are found unisexual flowers, e.g., Euphorbia (Dandathor).
This is a complex inflorescence. There are two opposite leaves in these plants and one inflorescence develops from each of the two opposite axils, e.g. Ocimum (Tulsi) and Salvia.