NCERT solutions for Biology Class 12 Plant Tissue Culture
In this article, we will discuss Plant Tissue Culture from Biology Notes for Class 12
The growth of cells, tissues, and organs, outside the organism’s body in artificial medium/ environment containing salts and nutrients (necessary for the growth of the particular organism), is called tissue culture. This is typically facilitated via use of a liquid, semi-solid, or solid growth medium, such as broth or agar. Tissue culture commonly refers to the culture of animal cells and tissues, with the more specific term plant tissue culture being used for plants. Depending on the cell type, the cells may be capable of a limited number of divisions or they may divide indefinitely. The term “tissue culture” was coined by American pathologist Montrose Thomas Burrows.
Broth: A liquid medium containing proteins and other nutrients for the culture.
Agar: It is also called agar. It is derived from the polysaccharide agarose, which forms the supporting structure in the cell walls of certain species of algae, and which is released on boiling. These algae are known as agarophytes (red algae). Agar is actually a jelly-like substance which is a mixture of two components: the linear polysaccharide agarose, and a heterogeneous mixture of smaller molecules called agaropectin. In chemical terms, agar is a polymer made up of galactose subunits.
Under appropriate conditions, the cultured tissues of some plants can often be made to regenerate new plants. The technique of plant tissue culture includes growing of plant tissues in a nutrient medium i.e. in vitro. Unorganized tissue or callus is cultured under this technique. These days, the term (plant tissue culture) is used for protoplast, cell, tissue, organ or whole plant culture in a nutrient medium under aseptic conditions.
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Inplant tissue culture technique the explants (i.e. cells, tissues or organs of a plant) are carefully separated and grown aseptically on a nutrient medium, under controlled conditions of light and temperature. The sterile growth medium or nutrient medium for culturing explants should typically contain sugar (or sugars) as energy and carbon source, mineral salts and growth substances and is usually solidified with agar.
Tissue culture is a method used for plant propagation in addition to other traditional plant-breeding techniques. Scientists found that any part of a plant grown in nutrient media under sterile conditions can give rise to a whole new plant. This property of plant cells to give rise to a whole new plant is called totipotency. It requires a nutrient medium that contains sucrose, inorganic salts, vitamins, proteins and growth regulators such as auxins and cytokinins.
Learn more about ‘Inplant tissue culture technique’ with Class 12 Biology animated videos.
How is Plant tissue culture done?
The first step is excising/ removing a small part of plant tissue, like the leaves, root or shoot of a plant then placing the cut-out part or explant in a suitable nutrient medium followed by allowing the explants to multiply and form a group of tissues(undifferentiated tissue) called callus. The callus is then allowed to multiply to form many plantlets which are then transferred to a different container for rapid multiplication. Finally, the developed plantlets are transplanted to the soil for normal growth. Therefore, tissue culture is performed using a small part of a plant to develop many plants and so is also called micropropagation. As all these plants are developed from the same part of the parent plant, they are genetically identical and called somaclones. Micropropagation, or tissue culture, is employed in the large-scale production of tomato, banana, and apple.
Plant tissue culture technique can also be used to propagate high-yielding disease-resistant varieties in a short span. Even if a plant is diseased, tissue culture can be used to get a healthy plant using the explant of the apical or axillary meristem. This is because the meristem is always free of disease and microbes. The tissue from where the growth originates in plants is referred to as the meristem. The meristem contains unspecialized cells called meristematic cells that continually divide, allowing the plant to grow. Aptly, meristem is derived from the Greek word merizein, meaning ‘to divide.’
Meristematic cells have often been compared to stem cells in humans. They divide rapidly, and their end role in the plant (leaf, stem, flower or root) has yet to be determined. Since they are unspecialized, their cell structure is very basic. They are small and tightly packed with small vacuoles, rudimentary chloroplasts, and thin cell walls. There are two types of meristem in plants: the apical meristem allows the plant to grow taller, while the lateral meristem allows the plant to grow wider. Culturing of meristems has been successfully carried out in plants such as banana, sugarcane, and potato.
In addition to the asexual propagation of plants, tissue culture is also used to mix two different species of plants that are otherwise sexually incompatible. Here, individual cells are isolated from each plant species and are placed in a culture medium. The cell wall gets digested in both cells which aid fusion of the two protoplasts of different species, resulting in a hybrid protoplast.
This process of developing a hybrid plant using somatic cells is called somatic hybridization. It was employed while fusing the tomato and potato plants to obtain a hybrid plant. In this manner, tissue culture, somatic hybridization, and other plant-breeding techniques provide a huge potential for manipulation of plants to produce new varieties, boost food production and enhance crops.
A detailed explanation of ‘How is Plant tissue culture done?’ from Biology Notes Class 12 is available.
Uses of Plant tissue culture
Tissue culture is used to develop thousands of genetically identical plants from one single parent plant known as soma clones by the process, known as micropropagation. The method offers an advantage over other methods as it can be used to develop disease free plants from diseased plants by using their meristems (apical and axillary) as explants. Since this method produces new plantlets by the score of thousands, it has been used extensively for production of commercially important plants including food plants like tomato, banana, apple etc. The most notable example of the application of micro-propagation was observed in the farming of orchids as it rose exponentially due to the availability of millions of plantlets thanks to tissue culture methods.
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