Flower is a group of reproductive organs of the flowering plants, which develops fruits and seeds and thus helps in forming new offspring of the plant. From morphological point of view flower is a highly condensed and modified shoot. Its function is reproduction.
In a typical flower there are four types of structures called floral leaves. These arc arranged in four whorls. Floral leaves are arranged on the swollen upper parts of flower stalk. The flower stalk is called pedicel and the swollen upper part is called Thalamus. In the thalamus are present nodes and highly reduced internodes. Floral leaves are borne on the nodes in whorls.
4 floral whorls
The four floral whorls taken from periphery to centre are as follows :
1. Calyx : It is the outermost whorl and floral leaves of this whorl are called sepals. Their function is that of protection of inner whorls and also that of photosynthesis when green.
2. Corolla : It is the second whorl of floral leaves which are called petals. These protect the inner two whorls and also function for attraction of insects for pollination.
Calyx and corolla are called accessory whorls of the flower. In some plants although two whorls are present they are not differentiated from one another. In such a case both whorls are called perianth and each part of the perianth is called tepal. If accessory whorls are absent in a flower it is called achlamydous flower (naked flower), if out of the two accessory whorls only one whorl is present it is called monochlamyd-ous flower and if both whorls are present it is called dichlamydous flower.
3. Androecium : This is third whorl of floral leaves and is the male reproductive organ of the flower. Each modified floral leaf is called microsporophyll or stamen.
4. Gynoecium (PistiI) : This is the last (fourth) central whorl of floral leaves
and is the female reproductive organ of the flower. Each modified floral leaf is called megasporophyll or carpel. Each gynoecium is made up of one or more mega-sporophylls (carpels).