Cation and total macroelement concentrations influence Ca uptake in micropropagated potato plantlets

Ca uptake by micropropagated 'Norland' potato plantlets was investigated in relation to cation and macroelement salt concentrations in modified Murash ige and Skoog (1962) basal media. Increased Ca:specific cations, by lowerin g NH4, Mg, or K, had little effect on the Ca content of plantlets grown on these media. Increased Ca:total cation ratio, by raising Ca from 3 to 6 mM in the medium, promoted Ca content of micropropagated plantlets. At equival ent Ca:total cation ratio, macroelement dilution increased the osmotic pote ntial of the medium, and had an even greater impact on plantlet shoot Ca co ntent. Root pressure, which is sensitive to variations in salt concentratio n, was probably the primary Ca delivery method to developing tissues since transpiration was limited in vitro. In vitro systems appear ideal for study ing some aspects of nutrient relationships of plants.