In this article we will discuss about the Tissue Culture in Plant:- 1. Subject-Matter of the Tissue Culture in Plant 2. Applications of Tissue Culture Technique 3. Advantages 4. Disadvantages 5. Future Prospects.
- Subject-Matter of the Tissue Culture in Plant
- Applications of Tissue Culture Technique
- Advantages of Tissue Culture
- Disadvantages of Tissue Culture
- Future Prospects of Tissue Culture in India
1. Subject-Matter of the Tissue Culture in Plant:
Plant cell culture is a rapidly developing technology which holds promise of restructuring agricultural and forestry practices. The tissue culture technique greatly reduces the labour and space requirement for producing new varieties and can markedly enhance propagation rates.
Theory of totipotency provides that it should be possible to produce an organism from any one nucleated cell of the body, since all the information needed to specify an organism is contained in its DNA. Consequent upon the pioneering research, plant tissue culture has found wide application in agriculture, horticulture, forestry and plant breeding.
Nature’s method of self-preservation in plant is mainly by seeds. This method is also the most economical one and, therefore, universally used for plant propagation. However, in several plant seeds are either not formed or they become inviable at an early stage or seeds are produced in small numbers.
Besides, several plants are cross pollinated and produce a promising progeny that show wide variation. Under such circumstances horticulturists use vegetative methods of propagation from underground stems, tubers, coms, rhizomes bulbs, etc. by cutting, layering, budding and grafting.
Plant tissue culture is being used to supplement the existing methods of sexual and asexual reproduction. The application of this technique is based on the observation that a single shoot tip when cultured on an appropriate nutrient medium, develops large number of shoots, identical to parents.
This method of clonal propagation is similar to the rooting of cuttings except the cutting used for tissue culture are much smaller often less than a centimeter in length (Fig. 25.1). Unlike the conventional methods where one cutting produces only one plant, by tissue culture thousands of plants can be produced in a short period from a single vegetative bud as in Chrysanthemum, gerbera, turmeric, teak, eucalyptus, etc.
The success of clonal multiplication in plants depends on the following:
1. Selection of mother plant:
Selection of mother plant with all desirable characters like high yield, good quality and disease resistance plays crucial role in tissue culture.
2. Collection of ex-plants:
A cut portion of plant organ or tissue used for initiation of an in vitro culture is called an explants. These can be shoot tips, root tips, leaves, tuber etc. Shoot tips are generally preferred.
3. Sterilization of ex-plants:
The ex-plants should be washed thoroughly with sterilizing agents, such as sodium hypochlorite, mercuric chloride solution and then washed with sterile distilled water before transferring to the nutrient media.
4. Preparation of culture media:
The appropriate composition of the nutrient medium largely determines the success of the cultures. In general, the media contains inorganic salts, vitamins, growth regulators (auxins, cytokinins, gibberellins), variety of carbohydrates, organic supplements such as yeast, malt extracts, coconut water and agar boiled in sufficient quantity of water.
Then it is sterilized in an autoclave and stored in media room. Now ready-made culture media are available with the scientific suppliers and they can be directly used for the purpose.
5. Transfer of ex-plants into flasks containing nutrient media:
This is done by experienced person in inoculation room under sterilized conditions. The sterilized ex-plants are transferred with the help of inoculation medium into the conical flask or jars containing culture media. Such flasks are kept in growth room where there will be controlled air, light, humidity and temperature.
When the tissues are placed on the culture medium within a few days a mass of cells called callus will develop due to active division of the tissue cells and within 3-6 week multiple shoots in bunches will appear from the callus.
6. Method of sub-culture and production of plants:
Multiple shoots are separated and transferred to the flask containing media in laminar airflow chamber. The medium is modified in such a way that roots and vegetative parts develop quickly. In one to three weeks young plants may develop from the cultured tissue.
7. Method of hardening:
This is a method in which the tissue culture plants developed in artificial media are habituated to grow in natural environment. Firstly these plants are taken out from nutrient media and washed thoroughly with water. Then these plants are grown in netted plastic pots filled with liquid nutrient medium and kept in green house for 6 – 8 weeks.
This is called Primary hardening. Afterwards the plants are transferred to polybags filled with potting mixture and grown under shaded house for 6 – 8 weeks. This is called Secondary hardening. After secondary hardening the plants are suitable for growing in farmer’s fields.
2. Applications of Tissue Culture Technique:
1. Large number of UNIFORM plants can be produced round the year, independent of season.
2. Techniques are also available to produce hybrid plants with combination of several desired characters (genetic manipulation) by tissue culture.
3. The plants so produced are uniform in growth similar to mother plant.
4. Where existing methods of propagation such as budding/grafting etc. are slow, complicated and costly.
5. Micro-propagation is carried out under aseptic laboratory conditions and, therefore, plants i produced are always free from seed borne diseases, however, subject to selection of healthy mother plant.
6. To preserve/store large number of germplasm of elite and endangered plants in small place without losing its originality.
7. Limited space is required to produce and maintain plants i.e., about 20 sft space is needed 1 produce 3,000 banana plants as against one hectare area by traditional method.
8. Plants of desired sex can be produced through tissue culture.
3. Disadvantages of Tissue Culture:
1. High investment.
2. Requires advanced level of skills and technology.
3. Needs commercial protocols (controlled environment and nutrient media).
4. Plants produced are comparatively costly.
5. Plants produced by tissue culture methods are observed to have poor photosynthetic activity because of abnormal leaf anatomy, malfunctioning of stomata, lack of epicuticular waxes and therefore, mortality in the field is high. These plants, therefore, must be exposed through the hardening process under green houses before planting in field conditions, to acclamatise them to open field conditions.
6. If the production process is not observed scientifically, the plants so produced may lack: quality e.g., with increased cycles of sub-culturing, many times genetically aberrant plant may emerge.
4. Future Prospects of Tissue Culture in India:
Tissue culture technique can be profitably employed for the production of elite clones and disease free propagules of desired plant type and a new era of green revolution in agriculture, horticulture and forestry can be brought in. In India present consumption level of tissue culture plants is negligible but the anticipated demand for tissue culture plants will be high with the commercialization of agriculture.
The first commercial tissue culture laboratory in India was set up by A.V. Thomas group of companies in Cochin. Since then, several industrial houses have set up tissue culture units.
These are Indo-American Hybrid Seeds, Bangalore, Harrison Malayalam in Chennai, Nath Seeds, Aurangabad, Godrej Plant Biotech, Hyderabad, Hindustani Agri-Genetics, Hyderabad, Proagro Seeds, Hyderabad, A.G. Biotech, Hyderabad, Agrindia Biotechnologies, Gaziabad. Jain Biotech Ltd., Jalgaon, Dharampur Sugar Mills Ltd., New Delhi, International Pulp and Fibres Inc., Gujarat, Kalptaru Irrigation System Ltd. Pune etc.
These units are engaged in production of tissue culture plants of fruit crops, vegetable crops, ornamental plants, forest trees and plantation crops.