Secondary product expression in vitro
The accumulation of secondary products in plant cell cultures in response to deliberate treatments to the chemical or physical microenvironment provides students with striking and explicit experimental evidence to confirm basic physiological principles. Secondary products such as vivid pigments, aromatic compounds, flavors, and bioactive phytochemicals can now be successfully accumulated in many plant in vitro cultures. Production of secondary products from plant tissue culture is based on the premise that the same valuable product produced in nature in an organ, fruit, or other tissue from a plant can be stimulated to accumulate in undifferentiated cells. The three long-standing, classic examples of commercially viable production of a secondary metabolite in vitro — ginseng saponines, shikonin, and berberine — each feature products that have diversified uses including medicinal applications. Ginseng is produced in large-scale root cultures, whereas the other two products are produced in highly colored cell cultures.