The adv antages of these systems square measure balanced by some necessary dis- vantages. For one, in heterotrophic and mixotrophic systems high concentrations of organic ingredients square measure needed within the nutrient medium (particularly sugar at a pair of or more), related to a high risk of microbic contamination. How, and to that extent this may be avoided are forbidden in Chapter three. different disadvantages square measure the difficulties and limitations of extrapolating results supported tissue or cell c- tures, to decoding phenomena occurring in Associate in Nursing intact plant throughout its development. it's invariably to be unbroken in mind that tissue cultures square measure solely model systems, with all positive and negative characteristics inherent of such experimental setups. To be realistic, an instantaneous duplication of in place conditions in tissue culture systems continues to be out of the question even these days within the twenty first century, and doubtless ne'er are. The organization of the genetic system and of basic cell structures is, however, primarily a similar, and so tissue cultures of upper plants ought to be higher suited as model s- tems than, e.g., cultures of alga, typically utilized as model systems in physiological or organic chemistry investigations. The domain cell and tissue culture is very broad, and essentially unspecif ic. In terms of sensible aspects, primarily 5 areas will be distinguished (see Figs. 1.1 , 1.2 ), that here shall be in short surveyed before being mentioned later at length.