Flower

A flower is a modified shoot in which the leaves are transformed into specialised reproductive structures. It is attached to the stem by a stalk called the pedicel. The swollen tip of the pedicel is the receptacle (also called the thalamus), on which all floral parts are borne.

Flowers vary enormously in size, shape, and colour — but all flowers follow the same basic plan: four sets of appendages (whorls) arranged on the receptacle.

Vertical section of a Hibiscus Flower

Flowers can be classified by their sex:

• Bisexual (perfect): Has both androecium and gynoecium (e.g., Hibiscus, Rose, Mustard)
• Unisexual (imperfect): Has only one of the two (e.g., Papaya, Watermelon)

A modified, compressed reproductive shoot of angiosperms bearing sepals, petals, stamens, and carpels, meant for sexual reproduction, is called a flower.

The swollen terminal part of the pedicel on which all floral whorls are arranged is called the thalamus or receptacle.

A circular arrangement of floral organs at the same level on the thalamus is called a whorl.

When calyx and corolla are not differentiated, the floral envelope is called the perianth.

Individual members of the perianth are called tepals.

The pattern of ovule arrangement in the ovary is called placentation. 

• Flower: A modified shoot and the reproductive unit of angiosperms.
• Structure: Consists of four whorls—calyx, corolla (accessory), androecium, and gynoecium (reproductive).
• Types by sex: Flowers may be unisexual (male/female) or bisexual (both present).
• Symmetry: Actinomorphic (radial), zygomorphic (bilateral), or asymmetric.
• Based on floral parts: Flowers can be trimerous, tetramerous, or pentamerous depending on the number of parts.
• Position of ovary: Hypogynous (superior), perigynous (half inferior), epigynous (inferior).