PLANT CELL CULTURE AND APPLICATIONS
The plant cell culture is based on a unique property of the cell, i.e., totipotency which may be defined as the ability of a plant cell to regenerate into whole plant on a defined artificial nutrient medium under the suitable physical conditions in the laboratory. In fact, it was Schwann who first drew attention to the fact that a single cell has the capacity to both grow and divide in a self regulatory fashion and that a single cell is also totipotent. This was stated in the famous 'cell theory' which was proposed in the beginning of 19th century by Schleiden and Schwann. Gottlieb Haberlandt, who is regarded as 'Father of Plant Tissue Culture', first attempted in 1902 tocultivate the mechanically isolated plant leaf cells on a simple nutrient medium. Though unsuccessful in achieving the growth and differentiation of the cultured cells, he has made several predictions in plant tissue culture like the concept of growth hormones, the use of embryo sac fluids, the cultivation of artificial embryos from somatic cells, etc. and indeed all of his predictions were found to be true as demonstrated by later researchers. In the first phase during the period 1902 - 1930s, attempts were made by several scientists to culture the isolated plant organs such as roots and shoot apices (organ culture). In the second phase during 1940s - 1970s, the extensive studies were undertaken to develop the suitable nutrient media to culture plant tissues, embryos, anthers, pollen, cells and protoplasts, and the regeneration of complete plants (in vitro morphogenesis) from cultured tissues and cells. Since 1980s, a new era has started involving the introduction of foreign genes into crop plants using cell and tissue culture systems to develop genetically modified (GM) or transgenic crops with improved characteristics, which may be responsible for the 'second green revolution.