Influence of Phenolic Acids on Ion Uptake

Abstract

The influence of naturally occurring phenolic acids on phosphate uptake by barley (Hordeum vulgare L. cv. Karlsberg) roots was examined using '3P-labeled phosphate. Without exception, all compounds tested, namely, benzoic, 2-hydroxybenzoic, 4-hydroxybenzoic, 3,4-dihydroxybenzoic, 3,4,5-trihydroxybenzoic, 4-hydroxy-3-methoxybenzoic, 4-hydroxy-3,5-dimethoxybenzoic, cinnamic, 2-hydroxycinnamic, 4-hydroxycinnamic, 3,4-dihydroxycinnamic, 4-hydroxy-3-methoxycinnamic, and 4-hydroxy-3,5-dimethoxycinnamic acids, inhibited uptake. (24,25).It has been demonstrated that in both higher plants (8) (12), and ferns (7). Through decomposition of plant material, rain leaching from leaves and bark. and exudation from roots a wide variety of phenolic acids may be introduced into the soil solution. Whitehead (23) sampled a variety of different soil types and reported the presence of 4-hydroxybenzoic, 4-hydroxy-3-methoxybenzoic, 4-hydroxycinnamic, and 4-hydroxy-3-methoxycinnamic acids as the free acids at soil solution concentrations equivalent to 5 X IO's M.The present study examines the influence of these naturally occurring phenolic acids upon inorganic phosphate uptake by barley roots. Concentrations employed were in the range reported by Whitehead (23). In the main, experiments were of short duration ranging from several minutes to 3 hr. MATERIALS AND METHODSBarley seeds (Hordeum vulgare L. cv. Karlsberg) were germinated and prepared for treatment according to the methods described by Epstein and Hagen (5). All experiments were performed with 4-day-old excised roots, approximately 3 cm long. After excision the roots were gently mixed in a large volume of distilled water, filtered through two layers of cheesecloth, and spun by hand in a cheesecloth bag to remove excess water.Root samples weighing 2 g were placed in 150-ml beakers containing 50 ml of solution, buffered at pH 7, containing 5 X I0-3 M Pi, 5 X 10-4 M CaCl2, and 0.05 pc of 3P-labeled phosphate. All experiments were performed at room temperature (23 C), and solutions were aerated continuously during the uptake period. The various phenolic acids which were added to the treatment solutions were dissolved in 1 ml of 95% ethanol. In most experiments, the final concentrations of phenolic acids experienced by the root tissue were 5 x 10' M, slightly in excess of the values reported by Whitehead (23) fer soil solution. In the preliminary kinetic experiments involving vanillic acid, concentrations ranged from 5 X 10-5 M to 1 X 10' M.The uptake of phosphate by root tissue was determined by the removal of 1-ml aliquots from the incubation medium at prescribed intervals. The radioactivity of each sample was determined in a Packard scintillation spectrometer, and uptake was determined by loss of activity from the solution.Preliminary experiments indicated that the uptake of phosphate, in both control treatments (in the absence of inhibitors) and vanillic acid treatments, had become linear within 5 to 10 min of immersion of the tissue in the phosphate solutions. In the com...

Influence of Phenolic Acids on Ion Uptake

“…In root tissue this involves a nonspecific increase in permeability to both cations and anions (3,5). Reference to the Goldman equation indicates that this increase in permeability and the resultant efflux of ions will affect E in two ways.…”

“…In a large number of reported cases, however, the modes of action of the allelopathic compounds (allelochemicals) are not understood. This paper reports further investigations into the mode of action of an important group of allelochemicals, phenolic acids.Earlier papers by Glass (3)(4)(5) have established that one ubiquitous group of phenolics, namely benzoic and cinnamic acids, are potent inhibitors of active K and Pi absorption by excised barley roots. The effect is readily reversible and the inhibitory capacity of the benzoic acids is strongly correlated with their lipid solubilities.…”

“…Earlier papers by Glass (3)(4)(5) have established that one ubiquitous group of phenolics, namely benzoic and cinnamic acids, are potent inhibitors of active K and Pi absorption by excised barley roots. The effect is readily reversible and the inhibitory capacity of the benzoic acids is strongly correlated with their lipid solubilities.…”

Boron, Lignification and the Origin of Vascular Plants‐a Unified Hypothesis

“…They argued that the effects of boron deficiency were direct and not mediated by accumulation of phenolic compounds since ' a reversibly impaired ATP-ase has been isolated from boron-deficient plants under conditions which should remove any phenolics bound to the membrane' (my italics). However, exogenous phenolics can markedly inhibit uptake of both anions and cations by roots of barley and soy-bean (Glass, 1973(Glass, , 1974Glass and Dunlop, 1974;McClure, Gross and Jackson, 1978). It remains to be seen how increased levels of endogenous phenols, brought about by boron deficiency (see pp.…”

Aspects of Rainforest Regeneration

“…Addition of chelators to nutrient solutions can reduce metal activity and uptake (Foy, Chaney and White, 1978) but Wallace et al (1974) suggest that uptake of metal chelates by snap beans may account for the high levels of Cu, Co and Cd in plants raised on chelator ammended soils. Glass (1973Glass ( , 1974 demonstrated that in short-term experiments, uptake of K and phosphate was inhibited by phenolic compounds which strongly infiuenced cell membrane potentials. Glass and Dunlop (1974) support the hypothesis that phenolic infiuence on ion uptake is mediated through direct non-specific effects upon cell membrane permeability.…”