FIGURE 2.

Effect of Al toxicity on common bean plants. High Al (70 μM AlCl₃) was added to (12 dpi) R. tropici-inoculated plants with active nodules (A) or to (12 days) fertilized plants (B), for 24 h or 7 days as indicated. Values are expressed relative to those from nodulated (A) or fertilized (B) plants grown in control condition (100%). Nitrogenase specific activity, as determined by the acetylene reduction assay, is expressed per nodule DW. Values are the mean ± SE for ten biological replicates from different plant sets. Student’s t-test was used to analyze the difference in each parameter between plants grown under stress vs. control treatments. Columns marked with star (^∗) represent significantly different means according to the statistical analysis (p ≤ 0.05).