11 Enhancement of Food Production - part 03 - Tissue culture

 

11 Enhancement of Food Production - part 03 - Tissue culture

Tissue culture :
  • Is actually a collection of different techniques. 
  • Technique of plant biotechnology. 
  • Here, isolated cells, tissues, organs are grown ‘in vitro’ on a solid/ liquid nutrient medium, under aseptic and controlled conditions of light, humidity and tempreature, for achieving different objectives.
  • Part of plant used in tissue culture is called explant. 
  • Plant tissue culture is based on principle of Totipotency which is an inherent ability of living plant cell to grow, divide, redivide and give rise to a whole plant. 
  • Haberlandt (1902 for the first time conceived this idea and developed the concept of in vitro cell culture (plant morphogenesis).
  • Medium contains all essential minerals, sources for carbohydrates, proteins and fats, water, growth hormones, vitamins and agar (for callus culture). 
  • Most commonly preferred medium for tissue culture is MS (Murashige and Skoog) medium.
  • Based on the nature of explant : There are three types viz- 
  1. Cell culture
  2. Organ culture and
  3. Embryo culture.
  • Based on the type of in vitro growth : There are two tyes viz.- 
  1. Callus culture (solid medium) and 
  2. Suspension culture (liquid medium).
Maintenance of aseptic conditions :
  • Aseptic condition is essential so as to avoid contamination by other harmful microorganisms.
  • It is accomplished by sterilization of : 
  1. glass ware (use of detergents, hot air oven)
  2. nutrient medium (by autoclave under constant pressure of 15 lb/sq inch for continous 20 minutes)
  3. Explant (by treatment of 20% ethyl alcohol and 0.1% HgCl2)
  4. Inoculation chamber (Laminar air flow) - by using UV ray tube for 1 hour before performing actual inoculation of explant on the sterilized nutrient medium
Other conditions maintained are :
  • Temperature - 180C to 200C
  • pH of nutrient medium 5 to 5.8 and 
  • aeration particularly for suspension culture.
  • In callus culture the solid medium is used.
  • The development and organisation of tissue is lost. 
  • Hence, the cells of explant, divide and redivide to form a mass of undifferentiated cells, called callus. 
  • It is maintained on solid medium.
  • Callus can be induced to form organs like root (rhizogenesis) and shoot (caulogenesis) and thus the plantlet. 
  • No shaker (agitator) is needed.
  • In suspension culture small groups of cells or a single cell are used as explant in the liquid medium. 
  • The liquid medium is constantly agitated by using shakers (agitators) so that there is constant mixing of medium and the explant.
  • Both the callus and suspension cultures die in due course of time. 
  • Therefore, subculturing is neccessary for continuation of the technique.
Micropropagation (Clonal Propagation) :
  • Organogenesis via shoots is considered as one of the most widely used commercial method of regeneration of plant.
  • Micropropagation is also known as clonal propagation.
  • It is the only process adopted by Indian plant biotechnologists in different industries, mainly for the commercial production of ornamental plants like orchids, Chrysanthemum, Eucalyptus, etc. and fruit plants like banana, grapes, Citrus, etc.

Do u Know ?
Applications of tissue culture :
  • There are various application of tissue culture in forestry, agriculture, horticulture, genetic enginearing, physiology, etc. 
  • The different applications of tissue culture include -
  1. Production of disease free plants and haploid plantlets
  2. micropropagation, production of secondary metabolites
  3. protoplast culture
  4. culture of rare plants
  5. somaclonal variations production of stress resistant plants, etc.
Advantages of microporpagation:
  1. Helps in rapid multiplication of plants.
  2. A large number of plantlets are obtained within a short period and from a small space.
  3. Plants are obtained throughout the year under controlled conditions, independent of seasons.
  4. Genetically similar plants (clones) are produced (formed) by this method.
  5. Desirable characters (genotype) and desired sex of superior variety are kept constant for many generations.
  6. Rare plant and endangered species are multiplied by this method and such plants are saved.
  7. With the help of somatic hybrids (cybrids), we are able to obtain new variety in short time span.

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