THE EFFECT OF pH ON THE BIOLOGICAL ACTIVITIES OF WEAK ACIDS AND BASES

Simon, E. W.; Beevers, Harry

doi:10.1111/j.1469-8137.1952.tb06124.x

Cited by 123 publications

(50 citation statements)

References 41 publications

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“…This suggests that SA°is the active species. On the other hand, the species that is active in the cytoplasm may be the charged species (SA-) with only SA°able to readily permeate the plasma membrane (15). If the cytoplasmic pH remains constant at about pH 7 regardless of the exterior pH (16), almost all molecules of SA°penetrating the plasmalemma would become dissociated in the cytoplasm.…”

Section: Resultsmentioning

confidence: 99%

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

Harper

Balke²

1981

Plant Physiol.

201

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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

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Section: Resultsmentioning

confidence: 99%

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

Harper

Balke²

1981

Plant Physiol.

201

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“…Our studies with red rice indicate that more attention should be paid to the pH of the incubation medium when working with nitrite and any other suspected dormancy-breaking agent (7,13) which can exist as a weak acid. Further, the degree of dormancybreaking activity of nitrite and nitrate has been shown to be very sensitive to small changes in afterripening which, in some cases, may not be detected by simply using the criteria of low germination of controls in water.…”

Section: Discussionmentioning

confidence: 99%

Seed Dormancy in Red Rice

Cohn¹,

Butera²,

Hughes³

1983

Plant Physiol.

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Sodium nitrite at 10 millimolar breaks dormancy of dehulled red rice (Oryza satira). While germination is light independent, low pH conditions (pH 3) are required for mimum response. Water and buffer controls at pH 3 remain dormant. The response to nitrite occurs at 25 and 30°C but is reduced at 20°C, although nondormant seeds germinate readily at this temperature. The contact time for response to nitrite is less than 2 h at the start of imbibition. Seeds imbibed first in water show reduced germination when subsequently transferred to nitrite. Dehulled seeds show little or no response to nitrate and ammonium ions.Intact seeds remain dormant in the presence of nitrite or nitrate unless partilly dry-afterripened. The pH dependence of nitrite sensitivity is reduced in intact, afterripening seeds. In highly dormant seeds, vacuum infiltration experiments suggest that the hull restricts uptake of nitrite.Red rice, an annual species, is a problem weed in rice production. Seeds of red rice shatter at maturity and can remain dormant in soil (4). The conditions that promote and break dormancy in this species are not well understood. Previously, it has been shown that freshly harvested seeds dry-afterripen at ambient temperatures. Both the hull and pericarp have a role in maintenance ofprimary dormancy in red rice. However, isolated embryos from freshly harvested seeds germinate readily (1). Primary dormancy ofdehulled red rice is broken by exogenously applied cytokinins, but there is no effect on intact seeds (2).Although there are many reports concerning the response of dormant seeds to nitrate, nitrite, and ammonium ions (e.g. 5, 11, and references therein), no information is available for red rice. As part of a comprehensive study of primary dormancy in red rice, the effects of these inorganic nitrogen compounds have been evaluated. MATERIALS AND METHODSMature, strawhulled red rice (Oryza sativa) was obtained from fields at the Rice Experiment Station, Crowley, LA, in 1979LA, in , 1980LA, in , and 1981 2 To whom correspondence should be addressed.sealed glass jars at -15°C. Seed moisture during frozen storage was 12%. Unless otherwise specified, seeds from the 1980 harvest were used, and germination tests were performed at 30°C for 7 d in dark incubators. Nine-cm-diameter glass Petri dishes containing one sheet of Whatman No. 3 filter paper and 10 ml of test solution were the standard germination system. A double layer oftissue paper was used to cover the seeds to insure uniform hydration. When required, intact seeds were dehulled by hand just prior to treatments. Five replicates of 30 seeds were used for each treatment. Experiments were repeated at least three times. Chemicals used were reagent grade and stored at room temperature. Test solutions were freshly prepared for each experiment. Dilute HCI or NaOH were used to adjust the pH of solutions.Procedures for experiments regarding the effects of light, dryafterripening, and vacuum infiltration were those employed previously (2). Effects of Light. Dehulle...

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“…For over 50 years researchers have recognized that ionization state may alter the biological activity of xenobiotics [1][2][3][4]. This observation is attributed to the un-ionized form crossing cellular membranes more readily than the dissociated moiety because of its lower polarity; hence, it is if often regarded as being more bioavailable for uptake.…”

Section: Introductionmentioning

confidence: 99%

Aquatic toxicity of sertraline to Pimephales promelas at environmentally relevant surface water pH

Valenti

Perez‐Hurtado

Chambliss

et al. 2009

Enviro Toxic and Chemistry

133

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Abstract-Researchers recognize that ionization state may influence the biological activity of weak acids and bases. Dissociation in aqueous solutions is controlled by the pK a of a compound and the pH of the matrix. Because many pharmaceuticals are implicitly designed as ionizable compounds, site-specific variability in pH of receiving waters may introduce uncertainty to ecological risk assessments. The present study employed 48-h and 7-d toxicity tests with Pimephales promelas exposed to the model weak base pharmaceutical sertraline over a gradient of environmentally relevant surface water pHs. The 48-h experiments were completed in triplicate, and the average lethal concentration values were 647, 205, and 72 mg/L sertraline at pH 6.5, 7.5, and 8.5, respectively. Survivorship, growth, and feeding rate (a nontraditional endpoint linked by other researchers to sertraline's specific mode of action) were monitored during the 7-d experiment. Adverse effects were more pronounced when individuals were exposed to sertraline at pH 8.5 compared to pH 7.5 and 6.5. The pH-dependent toxicological relationships from these studies were related to in-stream pH data for two streams in the Brazos River basin of central Texas, USA. This predictive approach was taken because of the scarcity of environmental analytical data for sertraline. The results of this study emphasized temporal variability associated with in-stream pH linked to seasonal differences within and between these spatially related systems. Relating site-specific pH variability of surface waters to ionization state may allow researchers to reduce uncertainty during ecological risk assessment of pharmaceuticals by improving estimates of biological effects associated with exposure.

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THE EFFECT OF pH ON THE BIOLOGICAL ACTIVITIES OF WEAK ACIDS AND BASES

Cited by 123 publications

References 41 publications

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

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

Seed Dormancy in Red Rice

Aquatic toxicity of sertraline to Pimephales promelas at environmentally relevant surface water pH

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THE EFFECT OF pH ON THE BIOLOGICAL ACTIVITIES OF WEAK ACIDS AND BASES

Cited by 123 publications

References 41 publications

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

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

Seed Dormancy in Red Rice

Aquatic toxicity of sertraline to Pimephales promelas at environmentally relevant surface water pH

Contact Info

Product

Resources

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

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