Fig. 1.

Effects of salicylic acid (SA), ZnPPIX, haemin, Fe (II) citrate, and ZnSO₄ pre-treatment on the concentration of thiobarbituric acid-reactive substance (TBARS) in alfalfa seedling roots subjected to 50 µM CdCl₂. Five-day-old seedlings were pre-treated or not with 1, 10, or 100 µM SA (SA1, SA10, and SA100; A), 10 µM SA (SA; B), 20 µM haemin (H), 20 µM Fe (II) citrate (Fe), 100 µM ZnSO₄ (Zn) alone, or the combination of treatments, in the presence (+) or absence (–) of 100 µM ZnPPIX for 12h, and then exposed to 50 µM CdCl₂ with or without 50% saturated aqueous CO solution (CO), 20 µM bilirubin (BR), or 20 µM Fe (II) citrate (Fe) for another 24h. The sample without chemicals was the control (C). Values are means ±SE of three independent experiments with at least three replicates for each. Bars with different letters are significantly different at P < 0.05 according to Duncan’s multiple range test.