Yan F, Feuerle R, Schaffer S, Fortmeier H, Schubert S
Institute of Plant Nutrition 330, University of Hohenheim, Fruwirthstrasse 20, D-70599 Stuttgart, Germany.
Plant Physiol. 1998 May;117(1):311-9. doi: 10.1104/pp.117.1.311.
Corn (Zea mays L.) root adaptation to pH 3.5 in comparison with pH 6. 0 (control) was investigated in long-term nutrient solution experiments. When pH was gradually reduced, comparable root growth was observed irrespective of whether the pH was 3.5 or 6.0. After low-pH adaptation, H+ release of corn roots in vivo at pH 5.6 was about 3 times higher than that of control. Plasmalemma of corn roots was isolated for investigation in vitro. At optimum assay pH, in comparison with control, the following increases of the various parameters were caused by low-pH treatment: (a) hydrolytic ATPase activity, (b) maximum initial velocity and Michaelis constant (c) activation energy of H+-ATPase, (d) H+-pumping activity, (e) H+ permeability of plasmalemma, and (f) pH gradient across the membranes of plasmalemma vesicles. In addition, vanadate sensitivity remained unchanged. It is concluded that plasmalemma H+-ATPase contributes significantly to the adaptation of corn roots to low pH. A restricted net H+ release at low pH in vivo may be attributed to the steeper pH gradient and enhanced H+ permeability of plasmalemma but not to deactivation of H+-ATPase. Possible mechanisms responsible for adaptation of plasmalemma H+-ATPase to low solution pH during plant cultivation are discussed.
通过长期营养液实验，研究了玉米（Zea mays L.）根系在pH 3.5与pH 6.0（对照）条件下的适应性。当pH逐渐降低时，无论pH为3.5还是6.0，都观察到了相当的根系生长。经过低pH适应后，玉米根系在pH 5.6时体内的H⁺释放量比对照高约3倍。分离玉米根系的质膜进行体外研究。在最佳测定pH条件下，与对照相比，低pH处理导致以下各项参数增加：（a）水解ATP酶活性，（b）最大初始速度和米氏常数，（c）H⁺ -ATP酶的活化能，（d）H⁺泵浦活性，（e）质膜的H⁺通透性，以及（f）质膜小泡膜两侧的pH梯度。此外，钒酸盐敏感性保持不变。得出的结论是，质膜H⁺ -ATP酶对玉米根系适应低pH有显著贡献。体内低pH条件下有限的净H⁺释放可能归因于更陡的pH梯度和质膜增强的H⁺通透性，而不是H⁺ -ATP酶的失活。讨论了植物培养过程中质膜H⁺ -ATP酶适应低溶液pH的可能机制。
