Natur-, Ingenieur- und Wirtschaftswissenschaften

The art of plant cell culture has made remarkable achievements in the past 75 years. Cell cultures can be derived now from almost all plant species. These suspension cells prove to be an excellent source of enzymes both for primary and secondary metabolic pathways and present an ideal system for the study of the metabolic fate of xenobiotic substances in plants. Moreover, the synthesis of secondary plant products by cellsuspension cul- tures is feasable. The production of natural substances used in medical therapy by means of cell cultures and fermentation techniques would offer considerable advantages over the production of these substances by agri- cultural techniques. Marinda citri/alia cells have been used as a model to explore the possibilities to produce secondary products (anthraquinones). Yields of these anthracene derivatives on a dry weight basis exceed the undifferentiated plant by a factor of up to 10. Similar yields with undiffer- entiated cells of other Rubiaceae have been achieved. In order to further increase the product formation of plant cells, a strategy should be adopted to produce mutants of haploid cells capable of higher production than the wildtype strains. For the detection and selection of high yielding cell clones and also differentiated plants, either as source for the establishment of cell cultures or for agricultural purposes, the use of radioimmunoassay systems is suggested. Plant cells can also be used for biotransformation processes in which a given product of low value is transformed by the cells into a desired pro- duct.