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The development of tissues of plants and animals through artificial means separate from the parent organism is known as tissue culture. Tissue culture is also known as micropropagation and helps in the development of disease-free plants. The growth of tissue is usually done in the laboratory in a liquid, solid, or semi-solid development medium such as agar or broth.
Tissue culture is a part of CBSE class 12 unit 8 Biology and Human Welfare chapter 9 Strategies for Enhancement in Food Production. The chapter carries a total of 10 to 12 periods and 4 to 5 marks.
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Tissue Culture: Types
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- Seed Culture:
In case of seed culture tissue from the plant (explant) is procured from an in-vitro derived plant and introduced in an artificial environment where it can multiply or proliferate. However in the beginning the tissue culture the explant should be sterilized in order to prohibit any damage to the cell.
- Embryo Culture:
In embryo culture, both mature and immature embryos can be used. The embryo is separated from the living organism and includes in-vitro growth of an embryo. Mature embryos are extracted from ripe seeds whereas immature embryos are extracted from the seeds that failed to germinate. The ovule, seed or the fruit are already sterilized in the beginning, hence further sterilization is not necessary in this form of tissue culture..
- Callus Culture:
Callus culture is the cultivation of modified plant cells developed in a medium of gel consisting of agar and certain particular nutrients required for the development of the cells.
- Organ Culture:
In case of an organ culture, a part of the plant be it leaf or shoot can be used as an explant in this form of tissue culture. There are several ways for organ cultivation which includes raft method, plasma clot method, grid method and agar gel method. This form of cultivation is helpful in preserving the functions and structure of any organism.
- Protoplast Culture:
A protoplast can be referred to as a cell which does not have a cell wall. Protoplast culture is a kind of tissue culture where the protoplast can be cultivated with the help of the hanging drop procedure or by micro-culture chamber. During the protoplast culture several places of plant development can be seen that include the growth of the cell wall, division of the cells and regeneration of a new plant.
Other types of tissue Culture
- Anther Culture
- Suspension Culture
- Pollen Culture
- Single Cell Culture
- Somatic Embryogenesis
Tissue Culture: Culture Medium
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The culture, growth medium or the nutrient broth is prepared by the process of sterilization. Through sterilization, all the microorganisms are removed from the culture medium (solution). This is done by heating under pressure for a specific period of time. However, it is made sure that the growth medium/culture solution consists of all the important microorganisms which are required for the development. These microorganisms are fungi, bacteria, algae, and protozoans. Agar is added to the culture medium to solidify it.
The chemical or synthetic medium used in the tissue culture is made up of certain inorganic compounds and inorganic salts. Various kinds of tissue cultures and living cells can also be a part of the growth or culture medium.
Selective media and Enriched media are two types of media that are known as special-purpose media. Enriched media is the media that contains nutrients that help in the development. Selective media contains those substances which are necessary for the development of selective organisms and stop the growth of all the other organisms.
Tissue Culture: Uses
Tissue culture is an essential part of production of identical, disease free platelets. Thousands of identical plants can grow from a parent plant known as the somaclones. This procedure is called micropropagation. It helps in the production of thousands of commercially essential plantlets since a single parent plant can develop thousands of plantlets such as food crops like tomato, banana, etc. This procedure is extensively used for the production of Orchids since thousands of plantlets arose through the method of tissue culture.
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Tissue Culture: Process
Tissue culture is a process in which the cultured tissue may consist of a single cell, a group of cells, one whole organ, or a part of it. Cells in the culture process may change their size, function, form or can even multiply and interact with other cells. These cells are also capable of doing a specialized activity. Tissue culture is also replaced with the term cell culture at times. In tissue culture, cells are taken from an organism and are revived in the culture medium. The culture medium contains necessary nutrients and energy sources. Step by step Tissue culture procedure:
- In the first step of tissue culture, also known as the initiation stage, the tissue is introduced into the culture. The required tissue is acquired and sterilized in order to prevent any form of contamination.
- In the second stage after the sterilization of the explant is complete, it is induced into the media that contains growth regulators as well as suitable nutrients which helps in the multiplication of the cells.
- In the third stage plant growth hormones are added for the roots to grow, as a result a complete plantlet can be obtained.
- Consequently growth hormones for shoot formations are added and are kept under observation for a week.
- When the plant begins to grow it is transported to the greenhouse in order to help them grow in a controlled environment and then transported again to nurseries to grow under natural conditions.
Tissue Culture: Examination of the Cultured Tissues and Cells
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Various ways of examining the live cultures are mentioned below:
- With the help of a microscope directly
- The photographs of movement are taken through the microscope directly.
- According to the objectives of the experiment the tissues, organs, or cells could be preserved, finished, or stained for further testing
- Samples can be spread on things like resin which can be cut into thin pieces. This will help in knowing the minute details under electron or light microscopes.
- Scientists by adding viruses or disease-causing microorganisms to try to know about the variations coming in the cells. They add vitamins, hormones, or drugs to know the reaction of cells.
Importance of Tissue Culture
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Tissue culture is an important aspect for preserving biodiversity and can be used for both plants as well as animals. It helps in conserving the tissue of endangered species. Incase of animals it is used for preservation of organs or tissues and incase of plants it helps in the alteration in the plant characteristics or increasing the yield of the plant. Through this technique plants produce the exact copy of themselves also known as the clones.
Advantages of Tissue Culture
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The advantages of tissue culture are stated below:
- Through tissue culture with the use of a little amount of plant tissue the plantlets can be acquired in a short span of time.
- The plants produced by this process are free from diseases.
- With the help of tissue culture plants can be grown throughout the year irrespective of the external conditions.
- In the case of tissue culture too much space is not necessary.
- Supply of new plants in the market increases with the help of tissue culture.
- This process is mostly used for the production of plants like Orchids, Dahlia, Chrysanthemum, etc.
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Tissue Culture: Sample Questions
Ques 1. What is the importance of Tissue culture? (2 marks)
Ans. There are many important functions of tissue culture. Some of them are mentioned below
- Used for developing plants without seeds, tubers, or bulbs.
- Preservation of endangered species and conservation of plants.
- Developing plants with certain desired characteristics
- Animal tissue helps in the preservation of organs, plant tissue culture helps in the preservation of plants or genetic modifications.
Ques 2. Can all plants be grown using the method of Tissue Culture? (2 marks)
Ans. Tissue culture is a method that can be used on any plant that has the characteristic of growing into a completely mature plant from a plant cell. This is also known as totipotency in other words. Tissue culture can be used for genetic modification or growing a plant with desired characteristics.
Ques 3. List the application of tissue culture. (4 marks)
Ans. Following are the list of applications of tissue culture:
- Tissue culture helps in the extraction of the clones of a plant through the process of micropropagation.
- It helps in the preservation of endangered species.
- It helps in increasing the production of healthy quality flowers, fruits, etc. by making the exact copy of the plants.
- Tissue culture helps in the production of plants when there is an absence of seeds and pollination such as Orchids and Nepenthes.
- Plants are grown under sterile conditions hence they are free from diseases.
- Regeneration of genetically modified plants from a single cell by cultivating it in a nutrient medium is possible through tissue culture.
- It also helps in the learning of the molecular basis of reproduction, physiological and biochemical mechanisms in plants such as vitro selection of stress tolerance plants.
- The method of tissue culture is also helpful in the induction of the polyploidy and chromosome doubling.
Ques 4. What kind of tissues do plants have? (3 marks)
Ans. Plants have many tissues but two main types of tissues are:
- Simple Tissues
- Complex Tissues
Simple Tissues are composed of a single kind of cell. Parenchyma and Collenchyma are examples of simple tissues. Parenchyma is made up of only parenchyma cells and collenchyma is made up of only collenchyma cells.
Complex Tissues are made up of more than one kind of cell. Xylem and Phloem are examples of complex issues.
Ques 5. How can one avoid contamination in tissue culture? (2 marks)
Ans. To avoid contamination in tissue culture one can use the following steps.
- Use antifungal or antibacterial antibiotics
- Through a sealed culture, the vessel prevent the entry of microorganisms
- Tissue culture must be properly covered, to avoid contamination
- The room must have proper ventilation and entry of sunlight must be proper
Previous Year Questions
Ques 1. Explain the relevance of “Totipotency” and “Somaclones” in raising healthy banana plants from virus infected banana plants. (2019)
Ans. The term ‘Totipotency’ can be referred to as the ability of an explant to produce a completely new plant. This characteristic helps the meristem tissue of a Banana plant to grow in a culture medium. As the meristematic cells are infection free and being totipotent they can develop the callus.
Some clones are developed through the process of tissue culture and are called ‘Somaclones’ because they are identical to their parent plant in terms of genetic and morphological aspects. These somaclones then develop into new plantlets that are infection free.
Ques 2. You have obtained a high yielding variety of tomato. Name and explain the procedure that ensures retention of the desired characteristics repeatedly in large populations of future generations of the tomato crop. (2018)
Ans. The procedure that would be used to ensure retention of the desired characteristics repeatedly in large populations of future generations of the tomato crop is micropropagation.
Micropropagation is the procedure to produce new plants within a short span of time through tissue culture. Under this technique a particular cell of the plant is isolated, multiplied in vitro and finally the regeneration of a whole new plant takes place. Every plant that is produced through micropropagation is identical in its characteristics and are known as somaclones.
Ques 3. (a) Write the two limitations of traditional breeding techniques that led to promotion of micro propagation. (b) Mention two advantages of micro propagation. (c) Give two examples where it is commercially adopted. (2016)
Ans. (a) Two limitations are:
- Traditional breeding failed to supply products at par with the demand.
- It didn't provide fast and effective ways to enhance the quality of crop production.
(b) Two advantages of micro-propagation are:
- It helps in the production of plants within a short span of time.
- Helps in the production of plants which are free from diseases.
(c) Two examples where it is commercially adopted are:
- Tomato
- Banana
Ques 4. Discuss the role of plant tissue culture in increasing food production. (2011)
Ans. Applications of tissue culture technique:
- This technique is applied for the rapid multiplication of desirable and rare plants.
- By this technique, an indefinite number of plants can be produced.
- From the culturing of virus-free tissues of the shoot apex of an infected plant, it becomes possible to obtain virus-free plants in sufficient stock. The tissue culture technique has been used to obtain virus-free potatoes and sugarcane.
- The technique (Embryo culture) is useful in overcoming seed dormancy, but also in producing viable plants from the crosses which normally fail due to the death of immature embryos.
- The technique has been applied for obtaining a large number of haploid and homozygous diploids.
- Somatic hybridization helps the fusion of cells belonging to different families.
- This technique is also useful for the genetic improvement of useful plants.
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