Inflorescence is defined as the complete flower head of the plant which includes stem, bract, stalk and flowers. It is a cluster of flowers at a branch of a stem or a system of branches that bears the flowers. It is being categorised on the basis of the arrangement of flowers on its main axis or peduncle. 

Inflorescence is broadly classified into 3 types namely Racemose, Cymose and Special or unique. This classification is based on the arrangement of the flowers in the pedicel. It is also classified according to the position of mature and young flowers namely, determinate and indeterminate. In a determinate inflorescence the youngest flowers are at the bottom of the rachis or axis while the determinate inflorescence it is the opposite. The details of the classification is as described below:

CLASSIFICATION OF INFLORESCENCE

As described earlier, it is basically of three types namely Racemose, Cymose and Special. These three are again classified into sub-types too they are as follows. 

RACEMOSE

The type of inflorescence that has a main axis which continues to grow and does not terminate in a flower but gives flowers laterally resulting in an arrangement of older and mature flowers at the lower side and the younger one at the upper sider. These are again of seven types namely Raceme, Spike, Catkin, Spadix, Corymb, Umbel and Capitulum. 

  1. Raceme – It is a type of inflorescence where the peduncle or the main axis is elongated with the flowers being pedicellate . It means that the flowers are having short stalks called pedicels. It is also known as racemoid inflorescence. It is an unbranched and belongs to the indeterminate type of inflorescence. For eg. Radish
  2. Panicle – It is the inflorescence has a branched peduncle and the each branch possess a raceme type of arrangement. It is much branched and may be determinate or indeterminate in growth. Many consider it to be a compound spike or a raceme itself. For eg. Neem
  3. Spike – It is the inflorescence that is very similar to raceme but the flowers are sessile in nature and has no stalk or pedicles. It is an unbranched and indeterminate type of inflorescence. For eg. Vasa or Malabar Nut. When the same inflorescence has branched peduncles and each of its branch possesses a spike then it is known Spike of Spikelets where the branch with possesses the flower is known as Spikelets
  4. Catkin – It is the inflorescence which has a thin, long and weak peduncle with sessile flowers. This inflorescence is also known as Amentum. These flowers unisexual which means they are either male (Staminate) or female (Carpellate). The main axis is always hanging or drooping or pendent in nature. For eg. Mulberry
  5. Spadix – It is the inflorescence which is having a thick, long and fleshy peduncle attached with unisexual and sessile flowers. It is often covered with a funnel shaped modified leaf known as Spathe. The flowers are covered with one or more green or colourful bracts. For eg. Maize.
  6. Corymb – This is an inflorescence where the peduncle is short and all the flowers are at the same level as the lower flowers have long pedicels while the upper ones are having a short one. This results in a flat topped appearance. The same when branched with each branch possessing a flower cluster, then it is known as Compound Corymb. For eg. Candytuft
  7. Umbel – It is the inflorescence which has the pedicels of all the flowers having same or similar length and arise from the same or common point. It is the characteristic feature of the family Scrophulariaceae which was earlier known as Umbelliferae. There is a whorl of bracts which form the involucre at the region where the stalk attaches to the flower and the point of origin. When the peduncle gets branched with each branch possessing a cluster of flowers, then such a type is known as Compound Umbel. For eg. Brahmi
  8. Capitulum – This variety is also known as Racemose Head or Anthodium. In this type, the growth of the peduncle is retarded and it becomes a broad, flattened concave or convex shaped structure. Here the flowers rise from a broad, flattened peduncle which makes a feel that the whole inflorescence is a single flower. If all the flower of the capitulum is same the it is known as homogamous. But when the younger flowers are in the centre (disc florets) while the older ar at the periphery (ray florets), then it is known as heterogamous. For eg. Sunflower.

CYMOSE

The second variety of inflorescence is the Cymose where the termination of the peduncle occurs in a flower. It is a determinate type of inflorescence. Here the main axis has a very limited growth and the lateral axis gets terminated by the growth of the flower. Here the upper portion has older flowers which is known as Basipetal succession. The Cymose is of three types namely Uniparous cyme, Dichasial cyme and Multiparous cyme. 

  1. Uniparous Cyme – In this variety the peduncle ends in a flower which produces lateral branch before ending in a flower. It is also known as Monochasial cymes. When all the lateral branches are developed on the same side, then such an arrangement is known as Helicoid cyme. Similarly, when a lateral branch develops on opposite sides, one followed by the other making them as lying alternate to each other, then it is known as Scorpioid Cyme. Example of Uniparous cymose is Saraca and Begonia.
  2. Dichasial Cyme – In this type the peduncle ends in a flower and from the basal part of the pedicel two lateral branches origin which also ends in a flower and the same is seen in the lateral branches too. It is also known as Biparous cymes. For eg. Jasmine.
  3. Multiparous Cyme – In this variety, there is emergence of several lateral branches that are arising from the base of the pedicels which also terminates into flowers like the earlier variety.  It is also known as Polychasial Cymes. For eg. Arka. 

SPECIAL OR UNIQUE

These are those inflorescence which are unique in characrer and don’t come in the above tow categories. Under this category, the Cyathium, Verticillaster, Hypanthodium and Mixed inflorescence are included. 

  1. Cyathium – This variety of inflorescence is seen in the family Euphorbiaceae. This is a specialised false flower where the bracts or the involucre fuses to form a cup shaped structure with the secretory glands lined at the margin. In the central part fo the cup a female flower is found which grows and comes out of the cup. The female flower is surrounded by small male flowers. 
  2. Verticillaster – This variety of inflorescence is seen in the family Lamiaceae or Labiatae. Here the inflorescence develops from the axil of each leaf. It is a condensed form of dichasial cyme with a cluster of flowers which are sessile in nature. Here the lateral branches arise from the main axil on which the flowers are found. 
  3. Hypanthodium – This variety of inflorescence is seen in the family Moraceae. Here the pedicel is modified into a narrow cup shaped structure. Here the axis becomes fleshy with a hollow cavity inside giving its shape. The base of the cup will develop the female flowers while its mouth develops the male flowers. This gives a fruit like appearance to the inflorescence. 
  4. Mixed – This variety is where the presence of both racemose and cymose variety of inflorescence can be observed that too on the same peduncle. They can be reclassified under different criteria like the pattern of branches, number of flowers and their arrangement, etc. For example Thyrsus of grapes and mixed spadix of Banana.

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