Morphological characters of Inflorescence & types

A group of flower is called inflorescence. Most flowers develop scorpioid cyme inflorescence. Small flower are inconspicuous. They collect together to form inflorescence to attract insects. The main axis of inflorescence is called peduncle. A long unbranched leafless peduncle arising from the ground level is called scape. Inflorescence may be terminal or axillary.

L Terminal inflorescence: In this case, the inflorescence forms at the apex of main branches. Main axis continues into axis of

inflorescence Example: Foxglove ‘

2. Axillary: In this case inflorescence forms on the branches. Example: pea

Solitary flower

Some flowers are solitary like rose. The solitary flowers have large corolla to attract insects. There are two forms of solitary flowers

  1. Terminal flowers: In this case, the flower borne at the apex of the main stem or its branch. Example: poppy.

  2. Axillary: In this case. the flower borne in the axil of a foliage leaf. Example: thalis

Types of Inflorescence

 

The inflorescence may be simple. compound, mixed or special types.

Simple inflorescence

The inflorescence in which branching of the main axis or peduncle is racemose or cymose is called simple inflorescence.

(a) Racemose inflorescence

The inflorescence in which main axis develops lateral flowers and continues to grow indefinitely unto last flower is called racemose inflorescence. The main axis is monpodial. The flowers are developed in acropetal succession. In this case, oldest flowers are home towards the base of inflorescence hut younger flowers are borne towards the apex. In some case, main axis becomes flattened. In this case, oldest flowers are.arranged towards the periphery and youngest flowers are arranged towards the centre. .[here are following types of racemose in florescence.

I. Simple raceme: The racemose inflorescence in which main axis is elongated and beam lateral pedicillate flowers is called simple raceme. Example: Linaria.

Types of racemose inflorescence

  1. Corymb: In this ease. main axis is short and pedicles of the older flowers are longer m it ped ides of the younger Ihmersare short. Therefore. all the fllowers come at the same level.

  2. Corymhose raceme: It is intermediate between simple raceme and con mb. In this case. the inflorescence is etay nib in the nok flowering stage. Hut later becomes siMple racetile due to elongation of its axis. Example: Brassica.

  3. Spike: The inflorescence in which main axis is elongated and hears sessile lateral flowers is called spike. The flowers may be bracteate or ebracteate. Example: Bottle brush, ginger .

  4. Spikelet: The dry spike which has one or few sessile flowers is called spikelets. Spike let is urrounded b a special bract at the base called ghillies. Example: grasses etc.

  5. Catkin: The spike with unisexual flowers is called catkin. The male catkin falls off as a whole after flowering. b thefemale catkin drops oil after fruitening.Example Mlilberr.

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  1. Strobilus: The unisexual spike with a large and membranous bract is called strobilus. In this case, flowers are crowded together. Example: hop

  2. Spadix: The special type of spike with main axis thick and fleshy bearing unisexual flowers is called spadix. The large prote2tive bract is known spathe. Example: Date palm .

  3. ale umbel: In this case, main axis above the first flower is a short and Mower appears to be arised from the same p it. The younger flowers are towards the centre and the older flowers are towards the periphery. Bract may or may not present. If bract present it forms involucre rounds the base of umbel. Example: cherry, Hydrocotyle.

Types of Raceme

  

  10.Capitulum or Head: The inflorescence in which main axis flattened to form receptacle and         flowers are crowed on it is called capitulum. The flowers are small and sessile. They are called florets.  The young florets are present at the centre of receptacle and older flowers are present towards the periphery. The receptacle has many overlapping bracts at the base called involucre. The flowers May be bracteate or ebracteate. The capitula may be homogamous or heterogamous.

  1. Homogamous: In this case, all tlov.ers are of same kind. Example: Sonchus

  2. Heterogamous: In this case, two types of flowers are present in the capittila. Example: Sunflower. Sunflower has two types of small flowers, disc florets and ray florets. The disc florets are present in the central region. They are tubular and bisexual. [he ray florets are present towards the periphery. They are pistillate or neuter.

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11. Hypanthodium: It is a modified form of capitulum. In this case, the receptacle grows upwards along its margin and form hollow pear shaped structure. It has apical opening guarded by scales. Unisexual flowers are developed on the inner surface of the hollow receptacle.

Hypanthodium

The male flowers are developed at apex near the opening. Example: peepal banyan.

Different Cymos inflorescence

(b) Cymose inflorescence

in this inflorescence the main axis soon ends in a flower. It gives one or two lateral branches or daughter axis, each of which ends in flower. This process repeated several times. The daughter axis arises in the axil of bracteoles. The flowers are borne in basipetal succession. In this case, the terminal flower is the oldest and the lateral flowers are younger. ‘Elie flower forms clusters in cymose inflorescence. The young film\ crs are present tmsards the periphery in cluster and old flowers are present in the central region. Such arrangement is called centrifugal. C muse inflorescence may he uniparous, biparous or multiparous.


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I. Uniparous or Monochasial cynic: In this case, the main axis ends in a terminal Him cr. Only one daughter axis is produced below this flower. ‘Elie daughter axis again ends a flower and gives another daughter axis. This process repeated several time. The daughter axis arises in the axil of bracteoles. Uniparous cynic may he coiled or spiral at first. But later it becomes straight to form a false central axis called sympodium. Therefore. it is also called sympodial cyme. There are two forms of uniparous chyme:

  • Scorpioid cyme: In this case, new daughter axis develops alternatively, i.e. right and left side. Example Henbane .

  • Helicoid cyme: In this case, new daughter axis develops on the same side. Example: Begonia.

  1. Biparous or Dichasial Cyme: In this case, the main axis ends in a terminal flower. It produces two daughter axes below this terminal flower. The daughter axis again ends in a flower and each gives two nev daughter axes. This process repeated several time. Sometimes, one of the two branches suppress at some point., Therefore, the biparous becomes uniparous. Examples: Ipomoea. strawberry etc.

  2. Multiparous or polychasium Cyme: In this case, main axis ends in a flower and produces a whorl of three or more daughter axes. Each of which forms branches in a similar way. Example:Euphorbia

  3. Cymose Head: The compact globose inflorescence haying groups of sessile scorpioid cymes is called cmose head. this case, flowers are arranged in groups or clusters. Each of Ahich is a scorpioid cyme. The main axis and spine daughter axes . are much reduced. Flowers are almost Sessile. Example: Acacia .Albizzia

Cymose Head

Compound inflorescence

The inflorescence in which main axis is branched and bears flowers in the same manner is called compound inflorescence. It has following types:

I. Compound raceme Or Raceme of racemes: In this case, main axis is racemosely branched and branches develops pedicillare flok‘er in a racemose manner. Example: Delphinium. Ao irregular branched raceme is called panicle. Example: Yucca.

  1. Compound spike or Spike of )

    case, main am of the inflorescence bears small or spikelets. Example: wheat, barely etc.

  2. Compound umbel or Umbel of umbels: Branched umbel is called compound umbel. The branches arise from the main axis form primary umbel. The flowers arise from each branch forms secondary umbel or partial umbel. Bracts may be present. If bracts are present at the base of primary umbel, these are called involucres. If bracts are present at the base of each secondary umbel, these are called involucel. Examples: Carrot. Coriander.

Compound Corymb or Corymb of Corymbs

 

  1. Compound Corymb or Corymb of Corymbs: The branched

  2. corymb is called compound corymb. Example: Cauliflower
  3. Compound Spadix: The branched main axis of spadix is called coin pound spad ix. Example: pahn

  4. Compound Capitulum: In this case, each capitulum consists of secondary capitulum. Example: Veronica

Mixed Inflorescence

The inflorescence in which both racemose and cymose branching occur is called mixed inflorescence. It has following forms:

I. Panicle of spikelets: In this case. spikelets are arranged on a

panicle branching. Example:oat

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  1. Raceme of cymes: In this case. paired secondary axis start as hiparous. But later it becomes uniparous which develop whorls of sessile flower forming verticillaster. Examples: Ocimatit

  2. Raceme of capitula: In this case, main axis is branched in a racemose manner and each branched terminates in a capitultim. Example: Erigeron.

  3. Compound umbel of cyathia:In this case, cyathia are arranged in umbellate manner. Example: Euphorbitt helioscoplo.’

  4. Panicle of short cymes: It is very dense and regular in shape. It is also called thyrsus. Example: vine

Special inflorescences

In some inflorescences, daughier axes are suppressed. So the flowers are crowded together in several groups. It is difficult to determine the type of infloreseence in them. Therefore, they are called special inflorescences. It has followimz types: .

1. Cyathium: It looks like a single flower. But in reality, it is an inflorescence. Many axes are reduced in it. Complete suppression of sepals and petals occur in flowers.

The main axis ends in a central reduced female flower. It is surrounded by a cup shaped inyolucre. Five scorpioid cymose Clusters of male flowers surround the female flower. The female

flower ripens first and then male ripens. This order of development is like cymose cluster. Example: Ettphorbia helioscopht.

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  2.Verticillaster: In this case, the bracts in the floral region are opposite. Each bract has a cluster of sessile flowers in its axis. The two clusters at the node form whorl like arrangements called verticillaster. The cluster of flowers is biparous cyme at first. Suppression of one or two branches occurs in it and it becomes uniparous. Example: Ocinttan

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      3.Umbellate Cymose Head: It is found in onion and garlic In this case, a long leafless stalk or scape arises in the midst of radical leaves. This seape bears cluster of flowers at its upper end. These flowers appear to form umbel. But in reality, they form helicoid cymose clusters. Therefore, such type of inflorescence is called umbellate cymose head.

 

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  1. Mirza Sanwal November 10, 2016

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