Characterization of the Inhibition of K⁺ Absorption in Oat Roots by Salicylic Acid

Abstract

The phenolic compounds salicylic acid (o-hydroxybenzoic acid) and ferulic acid (4-hydroxy-3-methoxycinnamic acid) inhibited K+ ("Rb+) absorption in excised oat (Avena sativa L. cv. Goodfield) root tissue. Salicylic acid was the most inhibitory. The degree of inhibition was both concentration-and pH-dependent. With decreasing pH, the inhibitory effect of the phenolic increased. During the early stages of incubation, the time required to inhibit K+ absorption was also pH-and concentration-dependent. At pH 4.0, 5 x 10-4 molar salicylic acid inhibited K+ absorption about 60% within 1 minute; whereas, at pH 6.5, this concentration affected absorption only after 10 to 15 minutes. However, at 5 x 10-' molar and pH 6.5, salicylic acid was inhibitory within 1 minute. The capacity of the tissue to recover following a 1-hour treatment in 5 x 10-4 molar salicylic acid ranged from no recovery at pH 4.5 to complete recovery at pH 7.5. The For many years it has been postulated that some plants exert an influence on neighboring plants through the production and release of toxic compounds (13,17). Some of these phytotoxins have recently been shown to inhibit ion absorption (4-6). The most commonly cited class of compounds involved in such toxic activity is that of phenolic compounds, especially derivatives of benzoic and cinnamic acid. Glass (5) efflux from yeast cells in the presence of SA. In a preliminary publication (7), we reported a similar effect of pH and SA on K+ efflux from oat roots. As pH of the medium fell, K+ efflux increased with 5 x 10-4 M SA present. Also, the herbicide 2,4-D inhibited K+ absorption in wheat roots more extensively as pH decreased (18). More recently, Jacobson and Jacobson (9) reported the same effect of pH in barley roots using TIBA. Thus, pH appears to be an important factor to consider when studying phenolic acids and their derivatives.The purpose of this research was to characterize extensively the action of the benzoic acid derivative, SA, on K+ absorption in excised oat root tissue. Our intent was to identify conditions required for inhibition of K+ absorption by SA and to provide the background for studying the physiological processes by which SA acts to inhibit absorption. We investigated the effects of pH, concentration of the inhibitor, and rapidity of action by the compound on K+ absorption. In addition, the absorption of SA itself was measured. We found that pH was a major factor in determining the degree of inhibition of K+ absorption by both SA and FA. We further observed that two parameters, pH and concentration of SA, interacted to produce complex effects on K+ absorption at various times of exposure to SA. MATERIALS

Differential Inhibition by Ferulic Acid of Nitrate and Ammonium Uptake in Zea mays L.

“…The presence of FA increased the initial net K+ loss from the roots during exposure to the low K, ammonium nitrate uptake solution and delayed the recovery to positive net uptake, but it did not alter the general pattem of the response. The implications of the observations are discussed for growth of plants under natural conditions and cultural practices that foster periodic accumulation of allelopathic substances.A deleterious effect of the phenolic compound FA2 on the uptake of phosphorus and potassium has been observed frequently (6,7,13,21 Little is known about the effect of allelopathic compounds on nitrogen uptake. In addition to probable effects of limiting the total nitrogen taken up, the possibility exists for differential effects on NO3-and NH4' uptake.…”

Atividade potencialmente alelopática de extratos brutos e hidroalcoólicos de feijão-de-porco (Canavalia ensiformis)

“…O grau de inibição proporcionado por determinado aleloquímico é dependente da sua concentração (Harper & Balke, 1981). Segundo Rice (1984), quando em baixas concentrações, as substâncias alelopáticas podem não ser inibitórias para determinadas espécies ou até mesmo apresentar efeitos estimulatórios, ao passo que em altas concentrações as substân-cias são completamente inibitórias.…”

Photosynthetic and Growth Responses of Olive to Proline and Salicylic Acid under Salinity Condition

“…SA application can influence ion uptake and transport (Harper and Balke, 1981)and gas exchange between plant and environment (Khan et al, 2003). The role of SA in defence mechanisms under both biotic and abiotic stresses has been shown in many plant species (Vlot et al, 2009;Ashraf et al, 2010;Montillet and Hirt, 2013).…”