Figure 5.

Effect of low nutrient-solution pH during plant cultivation on passive H⁺ transport across the plasmalemma of corn roots. Plasmalemma was isolated from 3-week-old corn roots grown at pH 3.5 (A) and 6.0 (B). The change of pH gradient across the plasmalemma was monitored by ΔA₄₉₂ of AO. Plasmalemma ATPase hydrolytic activity was initiated by addition of Mg-ATP (5 mm) to create a pH gradient across plasmalemma vesicles. For a reliable comparison, ATPase activity was stopped by addition of Na₃VO₄ (500 μm) after quenching had reached 0.0900 A units for both membranes. The resting pH gradient was collapsed by gramicidin (Gram, 5 μm).