PLANT TISSUE CULTURE The culture of plant cells or plant tissues in a synthetic culture medium under controlled aseptic conditions
is called “Tissue culture”. The controlled conditions give the culture a suitable microenvironment for the successful and rapid cell growth. Totipotency (capacity of plant cells or tissues to regenerate in to adult plants through division) is the genesis of “Tissue culture. For the first time tissue culture method was developed by G. ”Haberlandt (1902). He is often called Father of plant tissue culture, used culture medium without hormones. Skoog and Miller (1957) demonstrated the importance of growth hormones (auxins and cytokinins) in the plant culture medium. This is the most important success in plant tissue culture as it initiated the cell division and callus formation. During tissue culture, cells of small segments of plant tissue (
explants) undergo repeated division to form masses of cells called calli (sing. Callus). Each callus undergoes differentiation in to shoots and roots and forms a plant let. All plantlets regenerated from a plant material are identical and similar in the metabolic activities. Hence they are known as Clones. The method of raising the clones is called micro propagation or in vitro propagation (in vitro=culture in glass containers). After acclimatization, the plantlets are used for planting. The basic requirements for tissue culture laboratory are as follows: Space for Medium preparation (b) A sterile room (c) Laminar flow hoods (d) Glassware (e) Constant temperature room (f) A shaker system (g) chemicals including growth hormones. Selection of Explant Materials The excised portion of plant body from which explants is taken for callus culture, is called explant material. Any portion of plant body may be selected as explants material as per the requirement. It can be Tap root, Stem, basal plate, Leaf, Meristem, Endosperm, Nucellus, Germinating grains,Embryo,Stamen etc.. The culture and maintenance of individual plant cells in a liquid culture medium is known as
suspension culture or cell culture. The other method is solidified agar medium. Suspension cultures are used as model systems to study metabolic pathways in plant cells. They are used to regenerate identical clones from single cells. The suspension cultures are used in vitro mutation studies and also to isolate plant protoplasts for gene manipulation. Suspension cultures are also used for extraction of cellular enzymes and many secondary metabolites. The invitro culture of plant cells or tissues has many applications in crop improvement, preservation, and breeding and in industries. Tissue culture is employed in: a) Micropropagation b) Elimination of pathogens from plant materials) Germplasm storage d) Production of somaclonal variants e) Embryo rescue f) Production of haploids g) Production of artificial seeds h) Production of secondary metabolites I) Production of somatic hybrids j) Production of transgenic plants. Hitherto tissue culture operations were limited mostly to higher plants. When compared to higher plants, lower plants particularly algae have remained less worked out. However due to their importance as major sources of agar agar, algin, carrageenan etc.considerable attention has been given to improving the genotypes of economic algae. The basic and suitable material is callus in marine algae (seaweeds). Though relatively delayed in marine algae, tissue culture protocols have now been streamlined especially with regard to agarophytes.