Inflorescence : The mode of production of flowers on the peduncle is called inflorscence.
Peduncle : The main axis that get flowers and helps in reproduction is called peduncle.
Pedicels : In this the flowers are attached to the peduncle with their stalks are called pedicels.
Sessile : The sessile are the flowers in which pedicels are absent.
Terminal inflorescence : Terminal inflorescence is formed at the tip of the main stem. e.g. croton.
Axillary inflorescence : Axillary inflorescence is formed at the axil of the leaf, e.g. Dolichos.
Intercalary Inflorescence : Intercalary type of inflorescence is formed on internodes, e.g. Callistemon.
Different kinds of inflorescences are given below :
1. Racemose or Indefinite inflorescence
In this type of inflorescence the main axis does not terminate in a flower and there is no limit of flowers. Flowers open in acropetal manner. This is of two types—
(A) Pedicellate Recemose : This inflorescence can further be divided into following types—
(i) Simple Raceme : In this raceme the main axis is elongated and unbranched and bears flowers. Flowers are pedicellate. They are arranged in acropetal succession.
(ii) Compound Raceme : It is known as ‘Panicle’. In this the peduncle is branched and each branch produces pedicillate, bracteate flowers aeropetally. Thus each branch sesembles and single raceme. e.g. Yucca.
(iii) Corymb : In this the main axis is short and unbranched; and the flowers are on axis and are pedicellate. The flowers are placed at the same level at the top.
(iv) Umbel : Umbels are simple and compound. The primary axis is unbranched and shortened. At the tip, the axis bears a group of flowers. From a common point, the flowers spread out. Flowers are pedicellate. examples of simple umbels are Allium and of compound umbels are Daucus.
(B) Sessile Racemose Inflorescences :
(i) Simple Spike : In it the main axis is strong and unbranched. The number of flowers are there on the axis. They are arranged latterally, e.g. Amaranthus.
(ii) Compound Spike : It is a branched spike and grows indefinitely. Each structure looks like a flower and it is much reduced spike. Branches are called spikelets, e.g. Oryza, Triticum.
(iii) Catkin : In it the peduncle is long, weak and dropping. It is a spike like inflorescence. Flowers are sessile, small and bracteate.
(iv) Spadix : Spadix is simple and compound both. In simple spadix, the main axis is elongated, thick, fleshy and unbranched. Spadix with branched axes is present in compound spadix, e.g. Cocos.
(v) Heterogamous Head : This has two kinds of flowers or florets. Florets at the circumference are conspicuous with tongue shaped corolla. The central ones are with tubular corolla.
(vi) Homogamous head : In it all the flowers are similar in their shape and sex alligulate florets, e.g. Tagetus.
(vii) Compound Head : In compound head the axis is branched, and each branch bears a simple head. The example is Echinops.
2. Cymose or Definite Inflorescence
In Cymose or definite inflorescence the main axis and lateral branches end into a single flower and growth of each axis is checked. Cymes are of five types; namely—(a) solitary cyme (b) simple cyme, (c) monochasial cyme,
(d) dichasial cyme and
(e) polychasial cyme. All these cymes are described below.
(a) Solitary cyme : In solitary cyme the axis terminates in a flower, e.g. Datura.
(b) Simple cyme : After the termination of the axis in a flower, further growth is taken up by two branches, each producing one flower. The example is Jasminum.
(c) Monochasial cyme : This is also called uniparous cyme or sympodium cyme. In this cyme the main axis ends in a flower and it produces only one lateral branch ending in a flower.
(d) Dichasial cyme : This is also called Biparous cyme. In it, the axis terminates in a flower and stops growth. Two branches arise on either side. These branches also terminate in flowers. Lxora is an example of this cyme.
(e) Polychasial cyme : This cyme is also called multiparous cyme. In this the main axis terminates in a flower. It produces a number of lateral branches around. Each branch repeats the same kind of growth, e.g. Plumeria.
3. Mixed Inflorescence
It is partly recemose and partly cymose. It shows both the characters, e.g. Thyrsub.
4. Other Types of Inflorescence
There are several other inflorescences. These are
(a) Verticellaster (b) Cyathium and (c) Hypanthodium.
(a) Verticellaster : It is a condensed dychasial cyme developing from two axillary buds. It forms a ball like cluster at the nodes. Each node contains cyme. The example is Leucas.
(b) Cyathium : It is a single flower inflorescence. It is found in Euphorbiaceae members. In it each stamen represents a male flower and each pistila a female flower.
(c) Hypanthodium : It is a fruit-like inflorescence in which receptacle is fleshy and cup shaped, e.g. Fig.
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