Abstract
The aim of the present work was to determine the impact of Mg deficiency on K and Ca nutrition in the pastoral legume Sulla carnosa. Plants were grown in the presence of 1.50, 0.05, 0.01, or 0.00 mM Mg2+ during 3 (medium-term treatment) or 5 weeks (long-term treatment). After 3 weeks of treatment the optimum of growth was observed at 1.50 and 0.05 mM Mg2+, while with a long-term treatment the optimum was found only at 1.50 mM Mg-2. Gas exchange measurements decreased with decreasing magnesium concentration, and the optimum was recorded in plants grown in complete nutrient solution (1.50 mM Mg2+). Cotyledon Mg reserves and Mg use efficiency played a principal role in S. carnosa tolerance to the stress. Antagonisms between major cations were also noticed, mainly between Ca2+ and Mg2+, K+/Mg2+ antagonism being much lower. This antagonism depends on plant species, cation ratios, and treatment period.