Fig. 4.

Effect of low-pH and combined low-pH/Al treatments on rhizosphere pH at the distal elongation zone (top panel) and mature zone (bottom panel) of 4- to 5-day-old Arabidopsis thaliana roots. The low-pH and combined low-pH/Al treatments were imposed at time=0; the data recorded in the first 5 min before time=0 represent rhizosphere pH at pH 5.5. Error bars indicate ±SE (n=10–12 seedlings). Arabidopsis seedlings were conditioned in basal salt medium (BSM; 0.1 mM CaCl₂+1 mM KCl+0.2 mM MgCl₂, pH 5.5) for 20 min before treatments were imposed in unbuffered BSM.