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Cytokinin: Discovery and Functions, Morphogenesis, Practice Problems and FAQs

Cytokinin: Discovery and Functions, Morphogenesis, Practice Problems and FAQs

You have heard a lot about hormones. They are the chemical messengers which are required for the proper metabolic activities, growth and development. You know that hormones are present in plants also. But do you know which hormone is responsible for cell division in growing plants? Which hormone induces cell division or cytokinesis?

Fig: Shoot tip

Fig: Shoot tip

Yes, it is cytokinin that induces cytokinesis or cell division. It is an essential hormone that is present in the tips of roots and shoots, young fruits, leaves etc. It promotes growth and delays senescence. This hormone performs a variety of functions in the plant body. Let's take a deep dive into the details of cytokinins in this article.

Table of contents

  • Cytokinins
  • Discovery of cytokinins
  • Functions of cytokinins
  • Morphogenesis
  • Practice Problems
  • FAQs


Cytokinins promote cell division or cytokinesis and therefore, they are named as cytokinins. They are normally transported through xylem elements. Some synthetic cytokinins act as herbicides. They are found in the regions of rapid cell division, such as root apices, young fruits, shoot buds, etc.

Structure of cytokinins

They are basic in nature. They are chemically amino purines or phenyl urea derivatives. 

Fig: Structure of cytokinin

Fig: Structure of cytokinin

Discovery of cytokinins

Cytokinins were first discovered by C Miller, F Skoog, and co-workers during the 1950s. They identified cytokinins as factors that help promote cell division (cytokinesis). It was discovered as an adenine derivative. 

F Skoog’s experiment 

Cytokinin was discovered by F. Skoog while he was working on callus. Callus is described as the mass of unorganised cells.

Fig: Callus and F. Skoog

Fig: Callus and F. Skoog


Skoog observed proliferation of tobacco callus with the addition of cytokinin with extracts of vascular tissues, yeast extracts, coconut milk, and herring sperm DNA.

Fig: Experiment on tobacco proliferation

Fig: Experiment on tobacco proliferation


He observed that the test tube which had DNA showed maximum cell division.


Tube with DNA had a powerful cell division promoting effect. The material was further identified to be an adenine derivative. Kinetin, modified adenine, was identified from the autoclaved DNA. Kinetin can not be found naturally in plants. 


He concluded that the naturally occurring substances having similar structure to kinetin regulate the activity of cell division in the plants.

 Letham’s experiment 

Another chemical called zeatin was identified from the maize kernel. It is also an adenine derivative of cytokinin. It was the first identified naturally occurring cytokinin. Letham in 1963 isolated zeatin from immature corn kernels. He extracted zeatin from maize endosperm. Since the discovery of zeatin, many naturally synthesised (benzylaminopurine, thidiazuron) cytokinins have been discovered.

Types of cytokinins

There are two types of cytokinins as follows: 

Natural cytokinins

They are present naturally in the plants. Examples include zeatin. Kinetin is naturally present in herring sperm DNA. 

Synthetic cytokinins

They can be artificially produced. Examples include thidiazuron. 

Functions of cytokinins

Cytokinins perform the following functions:

  • They regulate cell division.
  • Cytokinin modifies apical dominance and promotes lateral growth.
  • Cytokinin delays senescence.
  • It promotes nutrient mobilisation.
  • It promotes chloroplast development.
  • They help to produce new leaves and adventitious shoots.
  • Promoting parthenocarpy

Regulates cell division

Cytokinin is necessary for cell division and promotes meristem growth. It is identified that in the presence of auxins, cytokinins stimulate cell division in non meristematic tissues. 

 Fig: Process of cell division

 Fig: Process of cell division

Excessive levels of cytokinin cause tumours. Tumour is a mass of rapidly proliferating cells. These cells undergo only division, not differentiation.

Fig: Tumours in plants

Fig: Tumours in plants

Overcome apical dominance and promote lateral growth

Cytokinin helps plants to overcome apical dominance. It initiates growth of lateral buds too. Cytokinin aids in producing bushy plants in this way. 

Fig: Lateral growth

Fig: Lateral growth

Delays senescence

Senescence is the process of aging in plants. Cytokinins delay senescence by preventing loss of RNAs, proteins and chlorophylls. It prevents the mobilisation of these chemicals. It is commonly called the Richmond Lang effect. It increases resistance to extremes of temperatures and diseases.

Fig: Delays senescence

Fig: Delays senescence

Promotes nutrient mobilisation

The nutrients move from one part to another part of the leaf. This is termed as cytokine induced nutrient mobilisation.

Fig: Nutrient mobilisation

Fig: Nutrient mobilisation

Promotes chloroplast development

Leaves treated with cytokinins have developed extensive grana, photosynthetic enzymes and chlorophylls. Cytokinin stimulates the activities of the enzymes associated with photosynthesis too. 

Fig: Chloroplast

Fig: Chloroplast

Helps to produce new leaves and shoots

Cytokinin promotes the production of new leaves and shoots.

Fig: New leaves and shoots

Fig: New leaves and shoots

Promoting parthenocarpy

It helps in the formation of parthenocarpic fruits. This was first reported by Crane. Examples include seedless watermelons and seedless grapes.

Fig: Seedless watermelon

Fig: Seedless watermelon


Morphogenesis is described as the generation of form. It is the generation of tissue organisation in animal and plant embryos. Auxin : Cytokinin ratio regulates morphogenesis. Morphogenesis can be regulated by altering the concentration of auxins and cytokinins. If there is no auxin and only cytokinin is present, growth is not shown in the plant tissues in tissue culture. If there is an intermediate concentration of auxin and cytokinin, the callus will be formed in the tissue culture. If there is high auxin and low cytokinin concentration, the roots will be formed in the plant tissues of tissue culture. If there is low auxin and high cytokinin concentration, shoots are formed normally in the tissue culture.

Fig: Regulation of morphogenesis

Fig: Regulation of morphogenesis

Practice Problems

Q1. Identify the hormone that promote lateral growth and overcome apical dominance.

A. Cytokinin
B. Auxin
C. Gibberellin
D. Abscisic acid

Solution:Cytokinin aids in the development of lateral shoots. It is an apical dominance controlling plant growth promoter. Apical dominance is a plant growth phenomena in which the main core stem grows faster than the peripheral stems. Auxins are inhibited by cytokinins. They aid in the regulation of apical dominance and the regulation of axillary bud growth. Auxin inhibits axillary bud growth and limits lateral branching when applied. However, cytokinin promotes the development of axillary buds, resulting in a bushy plant. Hence, the correct option is a.

Q2. How many hormones are responsible for delaying senescence?

Gibberellins, Cytokinins, Auxins, Abscisic acids

A. One
B. Two
C. Three
D. Four

Solution: From the given hormones above, two hormones delay senescence. These are gibberellins and cytokinins. Leaf senescence is the final stage of leaf development, here the leaves turn yellow and lose chlorophylls. This is delayed by gibberellins and cytokinins. Cytokinin promotes the production of new leaves and shoots. Hence, the correct option is b.

Q3. From the given statements, which statements are true for cytokinins?

Statement I : Cytokinin is a hormone that promotes cell division and delays the onset of senescence.

Statement II : Cytokinin is a term used for cell division.

 Statement III : Cytokinin helps in breaking seed dormancy.

 Statement IV : Cytokinin promotes lateral bud growth and control apical dominance

A. Only statement 1 is correct 
B. Statements 3 and 4 are correct
C. Statements 1 and 4 are correct
D. Statements 2 and 3 are correct

Solution: Cytokinin is a plant growth promoter whose key functions include cell division promotion, delay senescence (the process of plants ageing), and regulation of apical dominance. Apical dominance is a plant growth phenomena in which the main core stem grows faster than the peripheral stems. Hence, the correct option is c.

Q4. Why do leaves still remain green after plucking if they are dipped in cytokinin solution?
Solution: Cytokinin is a plant growth promoting hormone. If a leaf is immersed in cytokinin after being removed from a plant, it can stay green. Cytokinin enhances nutrient mobilisation while also delaying senescence (ageing). Here it prevents the loss of chlorophylls and hence the leaves remain green for a longer time.


Question 1. Why is cytokinin used in agriculture?
Answer: Cytokinin is used in agriculture because it is a one of the key hormones. It induces cell division and produces new leaves and shoots. It delays senescence. They are commonly used to increase the yield.

Question 2. Which hormones are responsible for morphogenesis?
Answer: Auxin : Cytokinin ratio regulates morphogenesis. Morphogenesis can be regulated by altering the concentration of auxin and cytokinin hormones. Morphogenesis is described as the generation of form. It is the process of generation of tissue organisation in animal and plant embryos.

Question 3. hat is the site of production of cytokinin?
Answer: Cytokinin is mainly produced in the apical meristem of roots. From here, cytokinin is transferred to the shoot tip via xylem.

Question 4. Name the first natural cytokinin discovered?
Answer: The first natural cytokinin discovered is zeatin which is found in the regions of rapid cell division, such as root apices, young fruits, shoot buds, etc.

YOUTUBE video:

Related Topics

Ethylene: Discovery and Physiological effects, Practice Problems and FAQs

Auxin: Discovery and Functions, Cholodny Went Theory, Practice Problems and FAQs

Gibberellin: Discovery, Functions and Uses, Practice Problems and FAQs

Photoperiodism: Photoperiodism in Chrysanthemum, Photoperiodic perception, Types of plants based on photoperiod, Practice Problems and FAQs

Abscissic acid: Discovery and Physiological effects, Practice Problems and FAQs 

Vernalisation: Types of flowers on the basis of season it flowers, Practice Problems and FAQs

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