Mineral nutrition of Gypsophila in vitro root culture

Mineral nutrition of panicled gypsophila roots (Gypsophila paniculata L.) ( Caryophyllaceae) cultivated in vitro in two media with different mineral co mposition, a classical Gamborg's B5 medium and a modified MH3 medium, was s tudied over a growth cycle of 28 days, by continuous measurement of mineral element consumption, without opening the culture flasks. The comparison be tween the total mineral element quantities consumed from media and those ab sorbed by roots at harvesting showed a good correspondence, proving the val idity of the technique used and the absence of insolubilized mineral forms in the in vitro culture media. The mineral element composition of the MH3 m edium was found to be better suited to Gypsophila paniculata root culture s ince all mineral nutrient elements are supplied in adequate quantities whic h are non-limiting and non-excessive. Culture on B5 medium showed that phos phorus (P) and copper(Cu) are probably the factors limiting growth and reve aled an ammonium (NH4+)/potassium (K+) ion antagonism. The in vitro roots, although uncoupled from the aerial part, behave like the roots of whole pla nts in several ways: the evolution of the medium pH corresponds to the form of the mineral nitrogen (N) consumed by the roots; sodium (Na) and chlorid e (CL) are barely consumed and may be considered as non-essential elements. Lastly, this in vitro root culture model makes it possible to explain that the absorption of Na and Cl by the roots of whole plants is probably depen dent on the transpiratory flow of the aerial part.