Notes, Exercises, Videos, Tests and Things to Remember on Inflorescence
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The mode of arrangement of flowers on the floral axis is known as an inflorescence. In angiosperms, a stalk of the flower is known as pedicel. Flower with pedicel become pedicellate flower and without pedicel become a sessile flower. The stalk of the inflorescence is known as the peduncle. Single flowered inflorescence is known as solitary inflorescence is known as solitary inflorescence and many-flowered inflorescences can be categorized into two major types;
If the floral axis does not terminate into a flower and its growth continues and give rise to the flowers laterally in acropetal succession (younger towards the growing tip and older towards the base) or In elongated floral axis or centripetal succession(younger towards the centre older towards the periphery) or if flattened floral axis than it is known as racemose inflorescence.
Pedicellate flowers arranged in acropetal succession in the elongated floral axis. Eg; Brassica Campestris
Sessile flowers arranged in acropetal succession in the elongated floral axis. Eg; Amaranthes, Achyranthes.
It is few small flowered spike surrounded by a pair of sterile glumes at the base. Eg; rice, maize, wheat.
In this type, the floral axis is weak and pendulous which bears unisexual sessile flowers in acropetal succession. Eg; Morus alba (Kimbu).
In this type, the floral axis is thickened and elongated which bears sessile flowers in acropetal succession and is surrounded by two too many spathes. Eg; Musa.
Head or capitulum:
In this type, the floral axis is flattened known as receptacle on which small flowers known as florets are developed in centripetal succession and is surrounded by a green involucre of bracts. Eg; Compositae
It is a special type of raceme in which the size of pedicels of the flowers go on decreasing towards the apex so that all the flowers are brought almost on the same level. Eg; Iberis Amara (candytuft)
The floral axis is short or reduced at the tip of which cluster of pedicellate flowers is developed. Eg; Coriandrum (Dhaniya)
If the floral axis terminates into a flower due to which its growth is checked and it gives rise to lateral branches successively which also terminate in the flowers, then it is known as a cymose inflorescence. Here, the flowers are arranged in a basipetal succession. On the basis of branching pattern, cymose inflorescence can be categorized into three types;
Monochasial or Uniparous cyme
If the floral axis after terminating into a flower gives rise to single lateral branch at a time which also terminates into a flower and follows the same pattern of growth, then it is known as monochasial cyme. Eg; Solanum
If the lateral branches successively arise on the same sides in a helix-like structure then it is known as helicoid cyme. If the lateral branches arise on the alternate side successively in a zigzag manner then, it is known as scorpioid cyme.
Dichasial or Biparous cyme
If the floral axis after terminating into flower gives rise to a pair of lateral branches at the line which follows the same pattern of growing then, it is called Dichasial cyme. Eg; Nyctanthes.
Polychasialor Multiparous cyme
If the floral axis after terminating into a flower gives rise to a cluster of lateral branches at the line which follows the same pattern of growth then it is called Polychasial. Eg; Calotropis