Effects of long‐term atmospheric CO₂ enrichment on the mineral concentration of <i>Citrus aurantium</i> leaves

summary Leaf mineral concentration of Citrus aurantium (sour orange tree) was measured at bi‐monthly intervals from 30 to 85 months of exposure in a long‐term study on the effects of a 300 μmol mol −1 enrichment of atmospheric CO 2 , under conditions of high nutrient and water supply. There were clear seasonal trends in the concentrations of most of the elements studied. There were initial decreases in the leaf concentrations of N and the xylem‐mobile, phloem‐immobile elements Mn, Ca and Mg, as well as a significant and sustained increase in the leaf concentration of B, and no changes in the concentrations of K, Fe, Na, P, S, Zn and Cu. Interestingly, the initial reductions in the leaf concentrations of Mn, N, Ca and Mg gradually disappeared with time.