Figure 5.

Al-induced secretion of oxalic acid from different sections of roots from cv Jiangxi (A) or cv Shanxi (B). Root segments excised from the root apex (0–5 mm) and the next segment (5–10 mm) were washed in 0.5 mm CaCl₂ solution, pH 4.5, and then transferred to a similar solution containing 0 or 100 μm AlCl₃. After 3 h, the root exudates were collected. The oxalic acid content in root apices was analyzed as described in text. Values are means of three replicates ± sd. Shown are the oxalic acid content in roots (white bars), oxalic acid secreted by the roots not treated with Al (black bars), and oxalic acid secreted by roots treated during Al treatment (shaded bars).