The Inflorescence

The reproductive shoot bearing group or cluster of flowers, that arrangement or specific pattern of flowers on the floral axis is called an inflorescence. The main axis of an inflorescence is called a peduncle.

Inflorescence could be of the following four types:

  1. Racemose Inflorescence
  2. Cymose Inflorescence
  3. Compound /mixed Inflorescence
  4. Special Inflorescence
Racemose inflorescence

In racemose the growth of inflorescence is unlimited. The arrangement of flowers is either acropetal or basipetal. Types of racemose inflorescence as follows:

    1. Raceme– The flowers are acropetally arranged and pedicellate. Example- Brassica species. (radish)
      • Note- Pedicellate flower- The flower bears a stalk or pedicle is called a pedicellate flower.raceme
    2. Spike– Acropetally arranged Sessile flowers. Ex. Achyranthes.
      • Note- sessile flower- the born directly on stem, that devoid of the stem is called sessile flowers.
    3. Catkin or amentum- These are acropetally arranged small and sessile flowers on a short, fleshy, and pendulous peduncle. Ex. Morus alba, willow, etc.
    4. Spadix– These are acropetally arranged small and sessile flowers on a short, fleshy peduncle and enclosed within a large bract called a spathe. Ex. Colocasia, Alocasia, etc.
    5. Spikelet– A very small spike with one or a few flowers. Ex. rice, bamboo.
    6. Corymb– The flowers arranged in the same horizontal plane or concave. The pedicle of the younger flower is shorter than the older one. ex. Ilberis amara (Candytuft)
    7. Umbel– It is a Raceme with a condensed peduncle in which flowers have equal lengths of the pedicle and are arranged in the shape of an umbrella. Ex. Centella asiatica (Brahmi)
    8. Capitulum (head)– externally reduced peduncle and centripetally arranged florets. Ex. helianthus, Dahlia.

inflorescence

Cymose Inflorescence
This type is also called a determinate or definite inflorescence. The growth of inflorescence is stopped with the formation of the first flower. Further growth of the inflorescence is caused by the formation of lateral branches. The arrangement of flowers is either basipetal or centrifugal. Types of Cymose Inflorescence as follows:
    • Monochasial or uniparous cyme: Differentiated into two types:
      • Scorpoid branching- successive branches appear alternately on two sides in a zig-zag pattern. There are two types of scorpoid branching-
        • Rhiphidium- the lateral branches appear in the same plain as the main axis, e.g. Solanum nigrum.
        • Cincinnus- lateral branches appear in angular direction e.g. Techoma
      • Helicoid branching: Successive branches appear on the same side. These are of two types:
        • drepanium – Lateral branches are the same in the plane as the main axis.
        • Bostryx- lateral branches appear in an angular plane. ex. Begonia
      • Dichasial or biparous cyme: two flower-bearing branches are formed below the terminal flower. e.g. Dianthus, jasmine.
      • Polychasial or multiparous cyme: more than two flower-bearing branches are formed below the terminal flower. e.g. Calotropis.
      • Cymose head: the peduncle is reduced to a circular disc, with sessile flowers, centrifugally arranged.
    Compound inflorescence/ Mixed inflorescence;

    in this type of inflorescence, the main branch is branched repeatedly and each branch may bear flowers in a racemose or cymose manner. These are the following types:

      1. Compound raceme eg. paddy, cassia
      2. Compound spike e.g. wheat
      3. compound corymb e.g. Pyrus
      4. Compound umbel, e.g. Coriandrum
      5. Compound capitulum e.g. Echinops

    Example of Mixed inflorescence: Musa paradisiac (banana)

    compound inflorescence

    Special types of Inflorescence

    These inflorescences do not fall under the categories described above. These are of the following types:

      1. Hypanthodium: In this type, the receptacle becomes pear-shaped, ex. banana, peepal, fig, etc.
      2. Cyathium: in this type, the five involucres are fused and forms a cup-like structure. e.g. members of Euphorbiaceae.
      3. Coenanthium: the receptacle becomes saucer-shaped. eg. Dorstenia benghalensis.
      4. Verticillaster: it is a modified condensed, dichasial cyme. e.g. salvia, ocimum, etc.

    You can also read:

    References: https://en.wikipedia.org/wiki/Plant_reproductive_morphology#Flowering_plants

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