Mineral Nutrition Laboratory, Soil and Water Conservation Research Division, Agriculture Research Service, United States Department of Agriculture, Beltsville, Maryland 20705.
Plant Physiol. 1970 Oct;46(4):538-42. doi: 10.1104/pp.46.4.538.
Effects of several organic acids on ion uptake and retention and on respiration in barley roots having low and high KCl contents were assayed by measurements of K(+), Na(+), Ca(2+), Cl(-), and oxygen uptake. Organic acids with high pK(a) values increase the permeability of roots to ions and decrease respiration when present in sufficient concentrations at pH 5 but have no inhibitory effects at pH 7. Absence of respiratory inhibition in short times and at lower organic acid concentrations, under conditions that immediately produce a permeability increase, indicate that the permeability change is not a result of respiratory inhibition. Effects of formate, acetate, propionate, and glutarate are attributed to entry of undissociated acid molecules into the effective membranes. Lack of a permeability increase with succinate, which has lower distribution coefficients to lipid solvents than do the aliphatic acids, can be explained by failure of sufficient amounts of the hydrophilic succinic acid molecules to penetrate the membranes involved. These experiments suggest that undissociated acid in root membranes can increase permeability of the roots.
采用测定 K(+)、Na(+)、Ca(2+)、Cl(-)和耗氧量的方法，研究了几种有机酸对低钾和高 KCl 大麦根吸收和保留离子以及呼吸的影响。在 pH 值为 5 时，具有高 pK(a)值的有机酸在足够浓度下增加了根对离子的通透性，并降低了呼吸作用，但在 pH 值为 7 时没有抑制作用。在短时间内和较低的有机酸浓度下，在立即产生通透性增加的条件下没有发生呼吸抑制，表明通透性变化不是呼吸抑制的结果。甲酸盐、乙酸盐、丙酸盐和戊二酸盐的作用归因于未离解的酸分子进入有效膜。由于脂溶性溶剂的分配系数低于脂肪族酸，琥珀酸盐没有增加通透性，这可以用足够数量的亲水性琥珀酸分子未能穿透所涉及的膜来解释。这些实验表明，未离解的酸可以增加根的通透性。
