Fig 2. Al-induced-secretion of malate (A and C) and citrate (B and D) by excised from C. grandis seedlings treated with different B and Al levels.

Malate and citrate secretion from excised roots were measured after 12 or 24 h treatment, respectively in 0.5 mM CaCl₂ + 0.5 mM AlCl₃·6H₂O (A and B) or 0.5 mM CaCl₂ solution (C and D), pH 4.1–4.2. Bars represent means ± SE (n = 4). Differences among four treatments were analyzed by 2 (B levels) × 2 (Al levels) ANOVA. Different letters indicate a significant difference at P < 0.05.