Inflorescence

The arrangement of flowers on the floral axis (peduncle) is called inflorescence. Inflorescence could be terminal or axillary. The stalk bearing an inflorescence is called peduncle.

Types of inflorescence

Inflorescence has been classified into two principal types depend upon the type of branching of peduncle and arrangement of flowers; Racemose and Cymose.

Racemose inflorescence: main axis is unlimited in growth, branched or unbranched. It never terminates into a flower and bears flowers in acropetal succession.

Cymose inflorescence: main axis terminates in a flower, hence is limited in growth. The flowers are borne in a basipetal order.

Differences between Racemose and Cymose inflorescence

Table showing differences between Racemose and Cymose inflorescence.
Table showing differences between Racemose and Cymose inflorescence.

Racemose

Cymose

The growth of the inflorescence is indefinite

The growth of the inflorescence is definite

The main axis does not terminate in a flower and continuous to grow

The main axis and its branches terminate in a flower

Flowers occur in acropetal order (oldest flower below and youngest near the apex)

Flowers in basipetal order (terminal flower is older)

The floral axis or peduncle is monopodial

The floral axis or peduncle is multipodial or sympodial

Types of Racemose Inflorescence

A. With main axis elongated

Table showing types of racemose inflorescence.
Table showing types of racemose inflorescence.

Type

Characters

Examples

Raceme

Main axis, which is elongated, bears stalked flowers

Brassica (mustard)

Spike

Like raceme, but flowers are sessile or unstalked

Achyranthes

Spikelet

Spike with one or few flowers called florets. Each spikelet has two sterile glumes and one fertile glume-bearing flower called lemma

Triticum (Wheat)

Catkin

Like spike but differs from having a long and pendulous axis, bearing unisexual flowers

Mulberry (Morus alba0

Spadix

Like spike with fleshy axis enclosed by one or several large and brightly coloured bracts called the spathes

Banana, Colocasia

B. With main axis shortened

Table showing types of racemose inflorescence.
Table showing types of racemose inflorescence.

Corymb

Lower flowers are long stalked and the upper ones have a short stalk, so they are placed almost at the same level

Candytuft

Umbel

Flowers have stalks of equal length and form a cluster from the same point

Coriander

C. With main axis flattened

Table showing types of racemose inflorescence.
Table showing types of racemose inflorescence.

Head or Capitulum

Flattened, more or less convex structure, the receptacle, on which the florets are arranged in a centripetal order. The whole inflorescence is surrounded by an involucre and bears only one or two types of flowers; inner disc florets and outer ray florets

Sunflower

Image showing types of Racemose Inflorescence.

Image Showing Types of Racemose Inflorescence.

Image showing types of Racemose Inflorescence.

Types of cymose inflorescence

Table showing types of cymose inflorescence.
Table showing types of cymose inflorescence.

Type

Characters

Examples

Monochasial cyme (uniparous)

Main axis terminates into a flower and one lateral branch axis develops from its base, which also ends in a flower

Cotton

Dichasial cyme (Biparous)

Axis terminates in a flower, two flowers arise laterally in each subsequent whorl and each branch ends in a flower

Dianthus, jasmine

Multichasial cyme

Axis terminates in a flower, more than two flowers arise laterally in each subsequent whorl, each lateral branch ends in a flower

Calotropis

Image showing types of Cymose inflorescence; (a) Monochasial, (b) Dichasial, (c) Polychasial.

Image Showing Types of Cymose Inflorescence.

Image showing types of Cymose inflorescence; (a) Monochasial, (b) Dichasial, (c) Polychasial.

Special types of inflorescence

Hypanthodium: main axis forms a cup-shaped receptacle with a small opening at the top. Flowers are enclosed within the cup in cymose groups. They are unisexual; male flowers are near the ostiole and fertile female flowers at the base of the cup, e.g. fig (Ficus).

Cyathium: single central female flower surrounded by many groups of male flowers. In each group the male flowers are borne in scorpioid manner. The inflorescence is surrounded by are involucre, e.g. Euphorbia, Pedilanthus.

Verticillaster: consists of biparous cyme ending in uniparous scorpioid cymes on either side. This arrangement is repeated on subsequent floral nodes to form the Verticillaster, e.g. Ocimum, Coleus.

Image showing special type of Inflorescence; Cyathium, verticillaster and Hypanthodium.

Image Showing Special Type of Inflorescence.

Image showing special type of Inflorescence; Cyathium, verticillaster and Hypanthodium.

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