mM and higher was clearly disadvantageous to the cells. The increase of all other elements, especially the macro -elements, also stimulated the growth of the calli. Due to the high concentration of minerals, MS medium is a very rich and -saline -medium and may be too salty to certain plant species. To avoid this problem, MS is often used with the micro elements in full concentration, but with the macro elements in respectively half or three-quarter of the concentration as originally described by the authors. Sometimes the original MS vitamines are replaced by the vitamins of Linsmaier and Gamborg B5 medium regarding the higher concentration of Thiamine in relation to the requirement of this vitamin by plants.