Lesson 39. Micro Propagation Methods


Micro-propagation is one of the important contributions of plant tissue culture to commercial plant propagation and has vast significance. The technique provides a rapid reliable system for a production of large number of genetically uniform disease free plantlets. Micro-propagation is the technique of developing plants from very small portion of plants such as shoots tip root tip, embryo, stem, pollen grain, callus or single cell. Plant tissue culture owes its origin to the revolutionary concept of totipotency of plant cell propounded by the famous German plant physiologist, Haberlandt in 1902. This technique has opened a vast scope for improve of fruits and plantation crops though micro-propagation, creating genetic diversity, germplasm conservation virus elimination, development of somatic hybrids and gene transfer.

Micro-propagation holds a great promise in fast multiplication of fruit and nut crops, which are invariably propagated asexually to meet the ever increasing demand for adequate and timely supply of clean planting material. It is possible through micro-propagation to produce millions of identical plants under controlled and aseptic conditions, economy of time and space, affording greater output and augmentation of elite, disease free propagules, safer and quarantined movements of germ plasm across nations. It also induces precocity in flowering, precision timing uniformity and often increases yield.

In fruit and plantation crops, comparatively difficult to micro-propagate, protocol have been developed for citrus, apple, banana, papaya, pineapple, grape, peach, plum, almond, walnut, strawberry, oil palm and date palm. In India, commercial exploitation of micro-propagation is limited to oil palm, strawberry and banana. It is primarily because of the highly heterozygous nature of the material which requires independent protocol for the different genotypes, problems of clonal fidelity, involvement of rootstock and overall costs. However, attempts are on to standardize protocol for crops like mango, cashew, walnut, oil palm, coconut, litchi, sapota and cocoa.

39.1.1 Micro-Propagation Types:

          (1) Meristem culture e.g. orchid, carnation

          (2) Tissue culture e.g. banana, date palm

          (3) Ermbryosis e.g. tobacco         

          (4) Embryo tube use e.g. orchid.


All the cells in an organism carry the same genetic information, yet show variations in expression,. Our knowledge of cell and tissue cultures has been developing with full swing, specially in bio-transformation, forestry, genetic engineering, morphogenesis, somatic hybridization, secondary metabolite production, hybridization, variety development and their conservation, maintaining pathogen free plants and rapid clonal propagation, totipotency, differentiation, cell division, cell nutrition, metabolism radio biology, cell preservation, etc. It is now possible to cultivate cells in quantity, or as clones from single cells; to grow whole plant from isolated meristems and to induce callus or even single cell to develop into complete plant either by organogenesis or directly by embryogenesis in vitro.

The production of haploid through tissue culture form anthers or isolated microspores and of protoplasts from higher plant cells has served as the basic tools for genetic engineering and somatic hybridization. Tissue culture technique helps to propagate plants of economic importance such as orchids and other ornamental plants in large numbers by their meristem culture or by other in vitro methods. This provides them virus-free plantlets, Propagation of valuable economic plants through tissue culture based on the principle of totipotency (every cell within the plant has potential to regenerate into a whole plant).

In plant breeding, embryo, ovary and ovule culture as well as in vitro pollination have been employed to overcome morphological and physiological sterility and incompatibility. In recent years, plant tissue culture technique is in increasing use for producing haploids from anthers or isolated microspores, and of protoplasts from higher plant cells and the recognition of the potential of these materials in genetics and plant breeding. One of the most significant developments in the field of plant tissues culture during recent years are the isolation, culture and fusion techniques which have their special importance in studies of plant improvement by cell modification and somatic hybridization.

Plant tissue culture technique is a boon in the studies of the biosynthesis of secondary metabolites and provides an efficient means of producing economically important plant products (fine chemicals). Plant tissue culture also provides raw material to pharmaceutical, cosmetic and confectionary industries examples are berberine, ginseng, shikonin and vanilla.


The technique has developed around the concept that a cell is totipotent when it has the capacity and ability to develop into whole organism. The principles involved in plant tissue culture are very simple and primarily an attempt, whereby an explant can be to some extent freed from inter-organ, inter-tissue and inter-cellular interactions and subjected to direct experimental control.

The most common culture in plant tissue is callus, which is wound tissue composed of undifferentiated, highly vacuolated and unorganized cells.

39.3.1 Callus Culture

For raising the callus tissues, a tissue culturist must have clear understanding of some basic principles. A cell from any part of the plant like shoot apex, bud, leaf, mesophyll cells, epidermis, cambium, anthers, pollen, fruit etc., when inoculated in a suitable medium under aseptic laboratory conditions can able to differentiate and multiply. This results into the formation of an amorphous mass of cells known as callus, which can be induced to re-differentiate on appropriate medium to develop embryoids which directly develop into the plantlets, eventually giving rise to a whole viable plant.

The term clone (from the Greek klon, meaning: a slip or twig suitable for plant propagation) was suggested by Webber (USA) in 1903 to explain those plants which were obtained by a sexual reproduction; it is even applied to DNA multiplication (cloning of genes in bacteria). In strict scientific sense, cloning means an organism obtained from a single cell through mitotic divisions.

 39.3.2 Meristem Culture

When a meristem is cultured in vitro, then it produces a small plant bearing 5 or 6 leaves. This could be obtained within a few weeks. Then the stem is cut into 5-6 small micro cuttings, which under favorable conditions, become fully grown plants.

39.3.3 Organ Culture

A body of higher plants has complex inter-relationships between different organs like root, shoot, apical meristem, leaf primordia, floral buds, ovary, ovule, anther lobs, pollen grains, fruit, seed, etc. In this method a particular organ is isolated and cultured under laboratory conditions in a chemically defined medium where they retain their characteristic structures and other features and continue to grow as usual. In organ culture, organs are not induced to form callus, therefore, it differs from the callus culture where the organization of the intact tissues is lost.

This technique provides and experimental system to define the nutrients and growth factors that are usually received by the organ from other organs of the plant body and from surrounding environment. It also helps us in understanding the inter-dependence of organs with respect to various physical and chemical growth factors including growth hormones. Organ culture technique also provides the knowledge about the various problems of morphogenesis and the sites of biosynthesis of specific metabolites and growth compounds. It may be used as a tool for improvement of various economically important crops.

Organ culture may be grouped into two major categories: vegetative organs (root culture, leaf culture, and shoot tip culture) and reproductive organs (complete flower culture, isolated ovary culture, isolated ovule and embryo culture, pollen mother cell culture, seed and fruit culture).

Last modified: Monday, 5 August 2013, 6:27 AM