The Components of Plant Tissue Culture Media I : Macro- and Micro-Nutrients

1. INORGANIC MEDIUM COMPONENTS

Plant tissues and organs are grown in vitro on
artificial media, which supply the nutrients necessary
for growth. The success of plant tissue culture as a
means of plant propagation is greatly influenced by
the nature of the culture medium used. For healthy
and vigorous growth, intact plants need to take up
from the soil:
• relatively large amounts of some inorganic
elements (the so-called major plant nutrients): ions of nitrogen (N), potassium (K), calcium (Ca),
phosphorus (P), magnesium (Mg) and sulphur (S); and,
• small quantities of other elements (minor plant nutrients or trace elements): iron (Fe), nickel (Ni), chlorine (Cl), manganese (Mn), zinc (Zn), boron (B), copper (Cu), and molybdenum (Mo).
According to Epstein (1971), an element can be considered to be essential for plant growth if:
1. a plant fails to complete its life cycle without it;

2. its action is specific and cannot be replaced completely by any other element;
3. its effect on the organism is direct, not indirect on the environment;
4. it is a constituent of a molecule that is known to be essential.
The elements listed above are - together with carbon (C), oxygen (O) and hydrogen (H) - the 17
essential elements. Certain others, such as cobalt (Co), aluminium (Al), sodium (Na) and iodine (I), are essential or beneficial for some species but their widespread essentiality has still to be established.

RITA®, temporary immersion system

source: www.cirad.fr


temporary immersion system for in vitro plant culture that ensures improved yields compared with culture on a gel medium. The RITA® system is now being used successfully for coffee microcuttings, coffee, rubber and banana somatic embryogenesis and potato microtuberization.

Characteristics

• Simple plant and medium handling• Improved nutrition: the plant is in close contact with the medium during immersion, and is covered by a capillary film throughout the remaining period• Marked reduction in asphyxiation• Complete renewal of the culture atmosphere on each immersion• Control of morphological processes by modifying immersion frequency and duration

Auxins

Nature of Auxins:

The term auxin is derived from the Greek word auxein which means to grow. Compounds are generally considered auxins if they can be characterized by their ability to induce cell elongation in stems and otherwise resemble indoleacetic acid (the first auxin isolated) in physiological activity. Auxins usually affect other processes in addition to cell elongation of stem cells but this characteristic is considered critical of all auxins and thus "helps" define the hormone (Arteca, 1996; Mauseth, 1991; Raven, 1992; Salisbury and Ross, 1992).

Functions of Auxin:

The following are some of the responses that auxin is known to cause (Davies, 1995; Mauseth, 1991; Raven, 1992; Salisbury and Ross, 1992).
Stimulates cell elongation
Stimulates cell division in the cambium and, in combination with cytokinins in tissue culture
Stimulates differentiation of phloem and xylem
Stimulates root initiation on stem cuttings and lateral root development in tissue culture
Mediates the tropistic response of bending in response to gravity and light
The auxin supply from the apical bud suppresses growth of lateral buds
Delays leaf senescence
Can inhibit or promote (via ethylene stimulation) leaf and fruit abscission
Can induce fruit setting and growth in some plants
Involved in assimilate movement toward auxin possibly by an effect on phloem transport
Delays fruit ripening
Promotes flowering in Bromeliads
Stimulates growth of flower parts
Promotes (via ethylene production) femaleness in dioecious flowers
Stimulates the production of ethylene at high concentrations

Above describes the effect of auxin on strawberry development. The achenes produce auxin. When removed the strawberry does not develop (Raven, 1992).

source:

http://www.plant-hormones.info/auxins.htm

Murashige and Skoog

Toshio Murashige is a professor emeritus of University of California Riverside in plant biology.

Folke K. Skoog (July 15, 1908 – February 15, 2001) was a Swedish plant physiologist who was a pioneer in the field of plant growth regulators, particularly cytokinins. Skoog was a recipient of the National Medal of Science.
Born in Halland, Sweden, Skoog emigrated to the United States during a trip to California in 1925, and was naturalized as a citizen almost a decade later. He competed, and finished fourth, in the 1500 meter race during the 1936 Summer Olympics. In 1936, he received his PhD in biology from Caltech for his work done with auxin, a plant hormone.
Skoog's professional career advanced significantly with his arrival at the University of Wisconsin-Madison in 1947. Carlos Miller discovered kinetin in 1954[citation needed], and benzyladenine and related compounds were later synthesized in Skoog's lab.
In 1962, Skoog and Toshio Murashige published what is probably the best-known paper in plant tissue culture; in a fruitless attempt to discover a yet-unknown plant growth regulator in tobacco juice for his doctoral thesis, Murashige and Skoog instead developed a greatly improved salt base for the sterile culture of tobacco. Now referred to as Murashige and Skoog medium, the final paper (Murashige, T. and Skoog, F. (1962) A revised medium for rapid growth and bioassays with tobacco tissue cultures. Physiol Plant 18: 100-127) is considered one of the most often-cited papers in biology. Now almost 45 years after its publication, M&S salt base remains an essential component in plant tissue culture.

History of Tissue Culture Techniques

History of Tissue Culture Techniques - The in vitro techniques were developed initially to demonstrate the totipotency of plant cells predicted by Haberlandt in 1902. Totipotency is the ability of a plant cell to perform all the functions of development, which are characteristic of zygote, i.e., ability to develop into a complete plant. In 1902, Haberlandt reported culture of isolated single palisade cells from leaves in Knop's salt solution enriched with sucrose.
The cells remained alive for up to 1 month, increased in size, accumulated starch but failed to divide. Efforts to demonstrate totipotency led to the development of techniques for cultivation of plant cells under defined conditions.
This was made possible by the brilliant contributions from RJ. Gautheret in France and P.R. White in U.S.A. during the third and the fourth decades of 20th century. Most of the modern tissue culture media derive from the work of Skoog and coworkers during 1950s and 1960s.

The first embryo culture, although crude, was done by Hanning in 1904; he cultured nearly mature embryos of certain crucifers and grew them to maturity. The technique was utilised by Laibach in 1925 to recover hybrid progeny from an interspecific cross in Linum. Subsequently, contributions from several workers led to the refinement of this technigue.
Haploid plants from pollen grains were first produced by Maheshwari and Guha in 1964 by culturing anthers of Datura. This marked the beginning of anther culture or pollen culture for the production of haploid plants.

The technique was further developed by many workers, more notably by JP. Nitch, C. Nitch and coworkers. These workers showed that isolated microspores of tobacco produce complete plants.
Plant protoplasts are naked cells from which cell wall has been removed. In 1960, Cocking produced large quantities of protoplasts by using cell wall degrading enzymes.
The techniques of protoplast production have now been considerably refined. It is now possible to regenerate whole plants from protoplasts and also to fuse protoplasts of different plant species. In 1972, Carlson and coworkers produced the first somatic hybrid plant by fusing the protoplasts of Nicotiana glauca and N. langsdorfii. Since then many divergent somatic hybrids have been produced.

A successful establishment of callus cultures depended on the discovery during mid-thirties of IAA (idole-3-acetic acid), the endogenous auxin, and of the role of B vitamins in plant growth and in root cultures.
The first continuously growing callus cultures were established from cambium tissue in 1939 independently by Gautheret, White and Nobecourt. The subsequent discovery of kinetin by Miller and coworkers in 1955 enabled the initiation of callus cultures from differentiated tissues. Shoot bud differentiation from tobacco pith tissues cultured in vitro was reported by Skoog in 1944, and in 1957 Skoog and Miller proposed that root-shoot differentiation in this system was regulated by auxin-cytokinin ratio.
The first plant from a mature plant cell was regenerated by Braun in 1959. Development of somatic embryos was first reported in 1958- 1959 from carrot tissues independently by Reinert and Steward.
Thus within a brief period, the tissue culture techniques have made a great progress. From the sole objective of demonstrating the totipotency of differentiated plant -cells, the technique now finds application in both basic and applied researches in a number of-fields of enquiry.

source: http://www.molecular-plant-biotechnology.info

Haberlandt ( The father of plant tissue culture )

The father of plant tissue culture is considered to be the German Botanist HABERLANDT who conceived the concept of cell culture in 1902.
"There has been, so far as I know, up to present, no planned attempt to cultivate the vegetative cells of higher plants in suitable nutrients. Yet the results of such attempts should cast many interesting sidelights on the peculiarities and capacities which the cell, as an elementary organism, possesses: they should make possible conclusions as to the interrelations and reciprocal influences to which the cell is subjected within the multicellular organism. Without permitting myself to pose further questions, I believe, in conclusion, that I am not making to bold a prediction if I point to the possibility that, in this way, one could successfully cultivate artificial embryos from vegetative cells".
Haberlandt, 1902.

HABERLANDT, when he embarked upon his attempt to culture plant cells was the first to consider culturing cells aseptically in a nutrient solution.
HABERLANDT did not realise that because photosynthetic cells are relatively differentiated their meristematic potential is not expressed easily and he did not know that this would require stimulating substances ie. plant growth regulators which were unknown at the time. Thus he chose to work with pallisade cells, pith cells, stamen hairs and stomatal guard cells. HABERLANDT cultured these cells in a simple organically enriched medium containing glucose under aseptic conditions and was totally unsucessful in all cases. His cells did not divide but were maintained in a living state for several weeks.
HABERLANDT failed to recognise that the meristematic cells of the plant body are basically heterotrophic and he did not know that the dedifferentiation of a cell into a meristematic state requires the presence of plant growth regulators.

source: http://users.ugent.be/~pdebergh/his/his2az1.htm

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