Figure 3From: Depletion of the heaviest stable N isotope is associated with NH4+/NH3 toxicity in NH4+-fed plants15N contents in tissues of spinach and pea plants. 15N content (μmol g-1 DW) calculated from the δ15N data, in shoots (A and C) and roots (B and D) of spinach (A and B) and pea (C and D) plants transferred from pH 7 to pH 6 (○) or pH 9 (●).Back to article page