Experimental systems based on plant cell and tissue culture are characterized by theuse of isolated parts of plants, called explants, obtained from an intact plant bodyand kept on, or in a suitable nutrient medium. This nutrient medium functions asreplacement for the cells, tissue, or conductive elements originally neighboring theexplant. Such experimental systems are usually maintained under aseptic conditions.Otherwise, due to the fast growth of contaminating microorganisms, thecultured cell material would quickly be overgrown, making a rational evaluation ofexperimental results impossible.