Know in one minute about tissue culture plants
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Introduction
Tissue culture plants
In general terms, tissue culture plants are plants obtained via tissue culture. Plant tissue culture is a general term used for the cultivation of plant cells, tissue, and organs in an artificially prepared medium under aseptic conditions. The term tissue culture is used for in vitro culture of plant cells, tissues as well and organs.
The Botanical Basis for Tissue Culture
The ability of plants to multiply asexually is the basis for plant tissue culture. Hence a complete plant can be developed in sterile lab condition that is in vitro condition from any part or tissue. The in vitro techniques were developed initially to demonstrate the totipotency of plant cells. Totipotency is defined as the ability of plant cells to divide and give rise to a complete plant. The Totipotency of plant cells is not only limited by the specialization or ploidy level but also the haploid gametophytic cells and triploid endosperm also express this potentiality under suitable culture conditions.
Major discoveries of plant tissue culture
- Trécul (1853) observed callus formation in some decorticated trees.
- Wiesner (1884) proposed a general theory that suggested the existence of organ-forming substances distributed in a polar fashion.
- Gottlieb (1902) Haberlandt developed the concept of in vitro cell culture.
- Hannig (1904) cultured embryos from several cruciferous species.
- Simon (1908) Regeneration of a bulky callus, buds, and roots from poplar stem segments.
- Kolte and Robbins (1992) successfully cultured root and stem tips respectively
- Went (1926) discovered the first plant growth hormone -Indole acetic acid.
2. Types of culture to obtain tissue culture plants
The following cultures are used to obtain the tissue culture plants.
1. Callus culture
A callus is an unorganized and dedifferentiated mass of cells originating from explants (a small part of a cut plant) under in vitro conditions. It is a loosely arranged group of parenchyma cells that developed from proliferating cells of parent tissue. The structure and growth habit of callus differs depending on the species to species. After the germination of the callus, it is subcultured and conserved by moving it to fresh media every 25-30 days.
2. Organ culture
In organ culture, any part of the plant like the root, stem, leaf, and flower is used as an explant. This technique is broadly used to retain or preserve the original structure and function of a particular part of the plant. It also supports to study of the growth, differentiation, and development of the plant part.
Methods used to perform organ culture
- Agar gel method
- Plasma clot method
3. Suspension culture
The culture in which single cells or small aggregates of cells multiply while suspended in an agitated liquid medium is called a suspension culture. It can also be known as cell Culture or cell suspension Culture.
4. Embryo culture
In embryo culture, the embryo is isolated and cultured under in vitro conditions. It can be done either by utilizing mature or immature embryos. The mature embryos are obtained from ripe seeds and the immature embryos are obtained from unripened or hybrid seeds.
The thing about this culture is the absence of any surface or treatment stress to the explant which is going to be cultured. This is because the whole ovule, seed, or fruit is sterilized before getting the embryo. This protects the embryo from any injuries that can arise during the process of surface sterilization.
5. Meristem culture
Meristems have the main function of the production of new cells and also the synthesis of protoplasm. Shoot meristem is made up of a group of certain dividing cells that are protected by the developing leaves.
6. Anther culture
The plant tissue culture in which haploids are produced by using anther is known as anther culture. First indicated by Guha and Maheswari in Datura plant.
7. Seed culture
In this type of culture, the explants are obtained from plants that are already cultured and grown under several in vitro conditions. Seed culture is best for plants that are sterile in nature.
8. Protoplast Culture
A cell without a cell wall is known as a protoplast. They are also called naked cells. Protoplasts can be isolated by mechanical and enzymatic techniques. The cultured protoplast goes through several stages that comprise the development of the cell wall, cell division, and regeneration of the whole plant. After cell division, the cells form a callus which is then subcultured for continuous growth.
3. Regeneration pathways
Tissue culture plants can be regenerated by following methods
1. Organogenesis
Organogenesis is the formation of organs from cultured explants. It is the process where the plant organs, either shoots or roots, are developed.
Types
1. Indirect organogenesis
The process in which plant organs are derived from a callus mass from the explant is termed indirect organogenesis.
2. Direct organogenesis
The production of direct buds or shoots from the tissue without the formation of the callus stage is called direct organogenesis.
2. Somatic embryogenesis
Embryogenesis is the process that consists of forming and developing embryos.
Types
1. Indirect somatic embryogenesis
It is a process where a callus is first produced from the explant, and then embryos are formed from the callus.
2. Direct somatic embryogenesis
In direct somatic embryogenesis, embryos are formed directly from a cell or small group of cells without the formation of a callus.
4. Method
Plant tissue culture includes two major methods:
- In vitro growth media types and suspension cultures.
- Different explant types- single cell culture, shoot and root cultures, somatic embryo culture, meristem culture, anther culture, haploid production, protoplast culture, somatic hybridization, embryo culture, ovule culture, ovary culture, etc.
Importance of Tissue culture plants
1. Plants with desirable quality can be propagated rapidly
Plant tissue culture helps us with the rapid production and large numbers of plants from small pieces of the mother plant in a short period of time. The technique also provides a way for the rapid multiplication of desirable and rare plants.
2. Disease-free plant production
Mass propagating of specific disease-free plants can be obtained and maintained by plant tissue culture. Plant tissues known to be free of the disease under consideration (viral, bacterial, or fungal) are physically selected as the explants for tissue culture. Tissue culture could be a useful way of circumventing or eliminating disease, which can accrue in stock plants.
3. Improvement of plant quality
The creation of superior varieties of agricultural crops is possible through the tissue culture method, which otherwise is not possible through conventional plant breeding methods.
4. Formation of new varieties
Breeding of new varieties can be possible via plant tissue culture.
5. High yield
This technique of plant tissue culture helps in increasing the branching and flowering, greater vigor, and higher yield, mainly due to the possibility of elimination of diseases.
6. True to Type production
A large number of true-to-the-type plants could be propagated within a short time and space throughout the year. Also, it may take about Two to Four months to produce a healthy planting material by tissue culture means, whereas a minimum of Six to Eight months is required for most species by the latest method of plant propagation.
7. Beneficial over conventional propagation
This technique does not need seed or any other conventional method of propagation and thus is very useful for those plants which are not propagated by the conventional method.
6. Types of media
1. Murashige and Skoog (MS) medium
This medium was invented by Toshio Murashige and Folke K. Skoog in 1962. It is mostly used in the tissue culture lab.
2. Linsmaier and Skoog (LS) medium
Linsmaier and Skoog 1965 developed this medium. The medium has some component as Murashige and Skoog with the addition of Linsmaier and Skoog vitamins.
3. Nitsch and Nitsch
J. P. Nitsch 1969 developed this medium. It contains some of the concentration of thiamine, biotin, and folic acid which supports anther callus.
4. White’s Medium
The white medium was developed by P. R. White in 1963. This was the earlier plant tissue culture media evolved for root culture. It possesses a lower concentration of salt and a higher concentration of MgSO4.
Q&A
1. What are tissue culture plants?
Tissue culture plants are the plants obtained via tissue culture that is they are grown from any part of the plants under controlled lab conditions that is in vitro culture.
2. What is plant tissue culture?
Plant tissue culture is a general term concerned with the cultivation of plant cells, tissue, and organs in an artificially prepared medium under aseptic conditions (Tissue Culture Association, 1984).
3. How to clone a spider plant using tissue culture?
- Collect 2-3 cm young shoots of the Chlorophytum borivilianum i.e spider plant.
- Sterilize the surface of the explant using Tween-20.
- Wash out the explant under running tap water.
- Again Sterilize the explant using 0.2% aqueous mercuric chloride (HgCl2) solution for 3-4 min.
- Wash out the explants to completely remove mercuric chloride.
- Prepare MS media with 3% sucrose and 0.8% agar.
- Place the explants containing MS media.
- When shoots reach a height of 2-3 cm transfer them to a rooting medium composed of Indole-3-butyric acid (IBA).
- The temperature of the room should be maintained up to 21-26°C, relative humidity of 51-55% and photoperiod 16hrs light and 8 hrs dark.
- When the roots of the plantlets reach up to 4-5 cm in length, remove them from the culture
- Wash these plantlets gently under running tap water. This is done to remove the agar stuck to the roots.
- Transfer the plants to a plastic cup and cover them with a glass jar to maintain moisture.
- After 30 days, plants will be ready to transfer to the greenhouse.
4. What is plant tissue culture used for?
- Plant tissue culture is used to produce a large number of plants very quickly.
- We Can grow rare or endangered Plants to increase the population.
- We can grow plants all year round.
- New plants grown are pests and disease-free.
- Genetic modifications can be introduced to large numbers of plant
5. How do the plant cells placed in a medium for tissue culture change?
Plant cells can be taken from many different parts of a plant like shoots, leaves, stems, roots, or undifferentiated cells. Mostly the cells are able to de-differentiate and go on cell division. Due to the process of cell division, the cells get transformed into tissue or organ like roots or shoots. Which leads to the concept of totipotency of plant cells.
Closing summary
In plant tissue culture, plant tissues are grown in vitro in an artificial media-controlled environment. The technique depends on the concept of the totipotency of plant cells. which refers to the ability of a single cell to develop into a whole organism by cell division. The capacity of cells to change their metabolism, growth, and development is also important and important to regenerate the whole plant. The medium used in plant tissue culture contains all the nutrients needed for the growth and development of plants. It is composed of macronutrients, micronutrients, vitamins, plant growth regulators, etc. MS medium is mostly used for the vegetative propagation of many plant species in vitro.
Written By: Pallavi Bhoyar
