Figure 6.

Effect of EGTA on mature cucumber hypocotyl cell walls' susceptibility to expansin. Nongrowing basal segments were frozen, thawed, abraded, pressed, and heated with water for 100 s in a microwave oven, and were pretreated with either 100 mm EGTA (pH 8.3) or distilled H₂O (pH 8.3) for 30 min at 25°C, washed with bathing buffer three times, and, finally, were hung under tension in the bathing buffer in an extensometer for 30 min, after which (indicated by an arrow) the bathing buffer was replaced with 0.1 mL of bathing buffer containing 2 mg mL⁻¹ of crude expansin. The basal segments that had been pretreated with EGTA could extend after adding expansin at 4.02 ± 0.73 μm min⁻¹ (solid line), whereas the basal segments that had been pretreated with distilled H₂O (pH 8.3) did not extend after adding expansin (dashed line). Curves are the mean of four independent experiments. Data are means ± se from four independent experiments.