Written By Taufiya Tazeen
Last Modified 22-06-2023

Inflorescence: Definition, Classification, Diagrams

Have you ever walked through a garden and seen a variety of plants with beautiful flowers? You might have noticed that flowers are arranged differently on the stems of each plant? Have you ever wondered what this arrangement is called? It is called inflorescence.

The inflorescence is the arrangement of flowers in a cluster on the stem of various plants. Each of these arrangements has its specific name. The arrangement helps to facilitate sexual reproduction in various ways. In this article, we will provide detailed information about Inflorescence.

Define Inflorescence

The arrangement of flowers in the floral axis is known as inflorescence. Inflorescence can also be defined as the group or cluster of flowers arranged on the stem which is composed of a main branch or cluster of branches. The main axis of inflorescence is called a peduncle.

Types of Inflorescence

An inflorescence is classified into different types based on the arrangement of flowers on a main axis or peduncle. There are broadly classified into four types, i.e. Racemose inflorescence (Indeterminate Inflorescence), Cymose inflorescence (Determinate Inflorescence), Special types of Inflorescence and Mixed Inflorescence.

Fig: Types of Inflorescence

Let’s learn more about these types of inflorescence:

Racemose Inflorescence (Indeterminate Inflorescence): In this type of inflorescence, the peduncle (flower axis) continues to grow. In racemose inflorescence, the branch does not terminate into a flower. The flowers are arranged laterally in an acropetal manner, i.e. older flowers are present on the lower side, and young flowers are arranged on the upper side.
Racemose inflorescence can be further divided into the following types:

Types of Inflorescence	Description	Examples
Raceme	1. The peduncle of the branch bearing inflorescence is elongated, and flowers are pedicellate; the inflorescence is called raceme type.	Mustard, Raddish
Panicle	1. When the peduncle is branched, and each branch bears a pedicellate flower arranged acropetally, then the inflorescence is called panicle or compound raceme type.	Delonix regia (Gulmohar), Azadirachta indica (Neem), Cassia fistula
Spike	1. In the spike inflorescence, the peduncle is elongated, but the flowers are sessile.	Achyranthes, Amaranthus
Spikelet	1. When the peduncle is branched, and each branch bears a spike inflorescence, then the small branch having a flower is called spikelet, and the arrangement is called spike of spikelet. 2. The main axis of this inflorescence is termed as rachilla (short axis), which bears one to many sessile or short-stalked flowers. 3. At the base of the rachilla, there are two boat-shaped sterile scales that are known as glumes, always placed one above the other on opposite sides. The lower ones are called first glumes, and the upper ones are known as second glumes. 4. A series of florets are present above the glumes.	Members of Poaceae (Gramineae or grass family).
Catkin	1. In catkin inflorescence, the peduncle is thin, long and weak. 2. The flowers are sessile and unisexual.	Mulberry, Betula, Oak
Spadix	1. In spadix inflorescence, the peduncle is thick, long and fleshy. 2. The flowers are small, sessile and unisexual and are enclosed by one or more green or colourful bracts.	Colocasia, Banana, Coconut, Maize
Corymb	1. In corymb inflorescence, the peduncle is short, and all flowers are present at the same level because the lower flower has a much longer pedicel than the upper one.	Candytuft, Cassia
Umbel	1. In umbel inflorescence, the flower stalks are more or less equal in length, and they arise from the same point. 2. The younger flowers are present in the centre, and the older ones are present in the periphery. 3. At the base of the flower stalk, there is a whorl of bracts forming the involucre called a simple umbel.	Centella
Compound umbel	1. A branched umbel is known as a compound umbel. 2. Usually compound umbel consists of both involucral and involucre of bracts.	Carrot, Coriander, Foeniculum, Cuminum
Capitulum or Racemose head	1. In capitulum inflorescence, the growth of the peduncle is reduced. 2. The peduncle becomes broad, flattened convex or concave and consists of small sessile flowers called florets. These florets are sessile flowers. 3. If the older flowers (ray floret) are present on the outer periphery, while the young flowers (disc floret) are arranged towards the centre, it is called centripetal order.	Sunflower, Tridax, Marigold

Fig: Racemose Inflorescence

2. Cymose Inflorescence (Determinate Inflorescence):
In cymose inflorescence, the peduncle ends with a flower. Here, the oldest flowers are thus terminal, and the young buds are lateral in position. This arrangement is therefore also known as the basipetal succession. Following are three types of cymose inflorescence:

Types of Inflorescence	Description	Examples
Uniparous cyme or Monochasial cyme	1. The peduncle terminates in flower producing lateral branch at one side. 2. It is of two types: 1. Helicoid cyme: In this type of inflorescence, the flower always develops only on one side, either on the left or right. 2. Scorpioid cyme: The flower arrangement is in an alternate manner such that the inflorescence appears in a zigzag manner.	Saraca, Heliotropism for Helicoid cyme and Boraginaceae, Begonia, Vine for Scorpioid cyme
Dichasial or biparous cyme	1. In this type, the peduncle terminates in flower and from the base of the peduncle, two lateral branches arise. 2. These branches also end in a flower.	Bougainvillaea, Jasmine, Teak, Mirabilis
Multiparous or Polychasial cyme	1. In this type, the peduncle terminates in flower, and many lateral branches arise from its base that also terminates in flowers.	Hamelia (Polychasial and helicoid type), Nerium, Calotropis

Fig: Cymose Inflorescence

Mixed Type of Inflorescence

In some plants, flowers are arranged in both racemose and cymose manner on the same peduncle and are called a mixed inflorescence. There are many examples of mixed inflorescence; some of these are given below with example:

Thyrsus: It is a cymose cluster borne acropetally on an axis, e.g., grape vine.
Mixed spadix: These are spadices with cymose inflorescence arranged acropetally on a fleshy axis having coloured spathes, e.g., banana.

Fig: Mixed Type of Inflorescence (Tulsi or Ocimum sanctum)

Some Special Types of Inflorescence

Lets us discuss some special types of inflorescence observed in various plants:

Verticillaster: We can find this type of inflorescence in the Labiatae or Lamiaceae family. This is basically a dichasial cyme that often becomes cincinal in its later branching. These cymes of sessile or nearly sessile flowers occur in leaf axils and often form a whorl of flowers at each node. Examples include Salvia, Ocimum, Coleus, etc.

Fig: Verticillaster

2. Cyathium Inflorescence: Cyathium inflorescence is the characteristic of Euphorbiaceae.

It is a special type of inflorescence, where the bracts or the involucre of bracts fuses to form a cup-shaped structure, known as cyathium.
The margin of this cyathium possesses secretory glands or nectar glands with bright colours.
Female flowers are found in the centre of the cyathium.
Small male flowers surround these female flowers.
They show protandrous development, i.e. male flowers mature first.

Fig: Cyathium

3. Hypanthium or Hypanthodium: This type of inflorescence is a characteristic feature of the genus Ficus. Examples include Banyan, Peepal, etc.

In this type of inflorescence, the peduncle is modified into a narrow, fleshy, hollow, globose, and cup-shaped receptacle with a narrow apical opening guarded by small overlapping bracts.
Many flowers are borne on the inner side of this hollowed receptacle.
Male, female, and gall flowers (sterile female flowers) are three types of flowers present in this inflorescence.
The female flowers develop at the base of the receptacle.
Male flowers develop towards the mouth of the cup.
Sterile female flowers are found in between these flowers.

Fig: Hypanthium

Significance of Inflorescence

The significance of inflorescence are as follows:

The flowers are positioned in a way that allows easy transfer of pollen grains and the optimization of the plant’s reproductive success during anthesis.
At the maturity of the fruit, it provides support and strength to the fruits prior to dispersal.
They play a very important role in phylogenetic and systematic studies.
The large and attractive morphology of inflorescence easily attracts insects that help in cross-pollination.
Inflorescence facilitates effective fruit and seed dispersal.

Summary

The inflorescence is a cluster of flowers arranged on the peduncle that is composed of the main branch or a complex order of branches. The inflorescence is the modified part of the shoot of flowering plants where flowers are developed that may involve the length and nature of the internodes and the phyllotaxis, as well as variations in certain aspects such as proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes.

FAQs on Inflorescence

Q.1. What are inflorescence and types?
Ans: Arrangement of flowers in the floral axis is known as inflorescence. The inflorescence is classified into two main types, Racemose inflorescence (Indeterminate Inflorescence) and Cymose inflorescence (Determinate Inflorescence).

Q.2. When the inflorescence axis of raceme is branched, it is called?
Ans: When the pedicle of raceme is branched and the lateral branches carry the flowers, the inflorescence is called a compound raceme or panicle.

Q.3. What is spike inflorescence in simple language?
Ans: A spike is an indeterminate inflorescence without branches. It is similar to a raceme but bears sessile flowers that are attached directly without stalks. Spike inflorescence is seen in the genus Achyranthes and Amaranthus.

Q.4. In which plant is Cymose inflorescence?
Ans: Bougainvillaea, jasmine, and teak are some examples of plants that bear cymose inflorescence.

Q.5. Give two importance of inflorescence.
Ans: 1. The flowers are positioned to allow easy transfer of pollen grains and optimise the plant’s reproductive success during anthesis.
2. At the maturity of the fruit, it offers support and strength to the fruits before dispersal.

We hope this detailed article on Inflorescence helps you in your preparation. If you get stuck do let us know in the comments section below and we will get back to you at the earliest.