Fig. 2

Effects of NaHCO₃, NaCl and vanadate on rhizosphere acidification. The roots of five-week-old in vitro shoot cultures were treated with water (pH 7.0) (a), 75 mM NaCl (pH 7.0) (b), 75 mM NaHCO₃ (pH 8.7) (c), and 75 mM NaHCO₃ plus 0.1 mM Na₃VO₃ (d, e) for 6 h. After the roots were washed with deionized water, the roots were carefully spread on the bottom of a culture dish and then covered with an agar sheet containing 0.006% bromocresol purple and 0.8% agar. In addition to bromocresol purple and agar, Na₃VO₄ was added into the whole agar sheet in panel d and into the right side of the agar sheet in panel e