Mineral nutrition of Gypsophila in vitro root culture

Abstract

Mineral nutrition of panicled gypsophila roots (Gypsophila paniculata L.) (Caryophyllaceae) cultivated in vitro in two media with different mineral composition, a classical Gamborg's B5 medium and a modified MH3 medium, was studied over a growth cycle of 28 days, by continuous measurement of mineral element consumption, without opening the culture flasks. The comparison between the total mineral element quantities consumed from media and those absorbed by roots at harvesting showed a good correspondence, proving the validity of the technique used and the absence of insolubilized mineral forms in the in vitro culture media. The mineral element composition of the MH3 medium was found to be better suited to Gypsophila paniculata root culture since all mineral nutrient elements are supplied in adequate quantities which are non‐limiting and non‐excessive. Culture on B5 medium showed that phosphorus (P) and copper (Cu) are probably the factors limiting growth and revealed an ammonium (NH₄ ⁺)/potassium (K⁺) ion antagonism. The in vitro roots, although uncoupled from the aerial part, behave like the roots of whole plants 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 chloride (Cl) are barely consumed and may be considered as non‐essential elements. Lastly, this in vitro root culturemodel makes itpossible to explain that the absorption of Na and Cl by the roots of whole plants is probably dependent on the transpiratory flow of the aerial part.