Ontogenetic Changes in the Chemical Composition of<i>Ricinus communis</i>Grown with NO⁻₃or NH⁺₄as N Source

Abstract

Ricinus communis L. var. Gibsonii was grown in Long Ashton nutrient medium with either 12mol m−3 NO−3 or 8.0 mol m−3 NH+4 as N source. Two plants from each N treatment were harvested twice a week and analysed for C, N, P, S, NO−3, SO2−4Cl−K+ Na+, Ca2+ Mg2+ and ash alkalinity. Statistical analysis of the data showed that the effect of age and N source was different for the chemical variables analysed. Thus [Na+] was unaffected by age or N source, and for both N sources [Mg2+] started at the same level and decreased at the same rate as the plants matured. With NH+4 as N source, [SO2−4] was higher than with NO−3, but did not alter with age. The concentrations, in mmol g−1 dry wt, of C, organic N, K+ and Ca2+ were different for the two N sources, but the levels of these variables altered with age in the same way for both N sources; i.e. there was no age x N interaction. In the case of P, NO−3, Cl− and COO−, however, age-related variations were different for the two N sources. It is concluded, inter alia, that [Na+] is determined by external [Na+] alone, and that K+, Ca2+ and Cl− are the inorganic ions actively involved in charge balance during ion uptake by the roots.