By Dr. Sylvia Mitchell, Contributor
Plants growing, in vitro, in the tissue culture laboratory at the Biotechnology Centre of the University of the West Indies, Mona. - Contributed
TECHNOLOGY IS 'the set of tools and techniques for controlling and changing one's environment'. In biotechnology these tools and techniques are based on biological principles and processes. Early biotechnologies (rum, wine, beer-making and so on) were in use long before the biological science behind the techniques was understood. Yeast growing in sugar-cane juice (making rum) or on newly-harvested grapes (making wine), without exclusion of other organisms, will ferment, and produce useful products. Bacteria, growing rapidly in large fermentors, can also produce a myriad of useful products.
Advances in science then made it possible to grow plants rapidly by growing them on artificial media, in vessels from which bacteria and fungi were excluded (called in vitro culture or tissue culture). Some of the scientific discoveries that made this possible are listed below:
Louis Pasteur, who lived from 1822-1895, at the request of a distiller from the north of France, began to examine why alcohol became contaminated with undesirable substances during fermentation. Pasteur discovered that each sort of fermentation was linked to the existence of a specific microorganism a living organism that one can study by cultivation in an
appropriate, sterile medium. This insight is the basis of microbiology. This
discovery destroyed the theory of spontaneous generation, which had held for
20 centuries, the theory that life could arise spontaneously in organic materials. In 1864 he developed the technique now called 'pasteurisation', a process by which harmful microbes in perishable food products are destroyed using heat, without destroying the food.
Haberlandt (1854-1945) is considered to be the father of plant tissue culture. He was the first recorded person to try to culture plant cells on an artificial medium. He used differentiated cells and they did not
multiply. He suggested however, that embryos may be cultured using embryo
sac fluid. A well-known embryo sac fluid is coconut water, which indeed has
been used to support growth of plants
in vitro.
Roots were the first organs to be cultured. This was accomplished
by White (1934) who discovered the importance of B vitamins as a culture
requirement. The isolated roots, however, only produced more roots. The
first tissue cultures are attributed to three scientists in 1939, who grew
long-term cultures of callus (disorganised proliferation of actively dividing cells).
The next major discovery was the
discovery of plant hormones,
first auxins (1935) and then cytokinins (1955). There are now many auxins
and cytokinins, and other plant hormones, that are known. The plant hormones
are growth regulators influencing both cell elongation and division, encouraging either shoot or root growth, and a myriad of other growth processes in plants. The stimulatory properties of coconut water is partly due to a natural cytokinin, zeatin riboside. Varying the ratio of auxin to cytokinin in the artificial medium, in the glass vessels, regulates the amount of shoot or root growth produced from plant explants. Even a single plant cell has been found capable of regenerating a whole plant.
Since these discoveries, results have come fast and furious, resulting in a technology: used in laboratories to study plant growth, as an important step in plant transformation, in industry to produce elite plants for farmers and horticulturists, and in industry to synthesise significant amounts of useful compounds including antimicrobial compounds, antitumor alkaloids, food flavours, sweetners, vitamins, insecticides and enzymes. An example of the success of this biotechnology is to consider that in 1960 Morel produced four million genetically identical plants from one orchid bud in one year. In 1988, Europe had an estimated 248 commercial tissue culture labs, with 37 of these producing more than one million plantlets each.
Dr. Sylvia Mitchell, scientific officer, Biotechnology Centre, University of the West Indies, Mona, email: smitchel@
uwimona.edu.jm.
