Abstract
Short-term ion uptake into roots of Limnobium stoloniferum was followed extracellularly with ion selective macroelectrodes. Cytosolic or vacuolar pH, together with the electrical membrane potential, was recorded with microelectrodes both located in the same young root hair. At the onset of chloride, phosphate, and nitrate uptake the membrane potential transiently decreased by 50 to 100 millivolts. During Cl− and H2PO4− uptake cytosolic pH decreased by 0.2 to 0.3 pH units. Nitrate induced cytosolic alkalinization by 0.19 pH units, indicating rapid reduction. The extracellular medium alkalinized when anion uptake exceeded K+ uptake. During fusicoccin-dependent plasmalemma hyperpolarization, extracellular and cytosolic pH remained rather constant. Upon K+ absorption, FC intensified extracellular acidification and intracellular alkalinization (from 0.31 to 0.4 pH units). In the presence of Cl− FC induced intracellular acidification. Since H+ fluxes per se do not change the pH, recorded pH changes only result from fluxes of the stronger ions. The extra- and intracellular pH changes, together with membrane depolarization, exclude mechanisms as K+/A− symport or HCO3−/A− antiport for anion uptake. Though not suitable to reveal the actual H+/A− stoichiometry, the results are consistent with an H+/A− cotransport mechanism.
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Selected References
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- Blevins D. G., Hiatt A. J., Lowe R. H. The Influence of Nitrate and Chloride Uptake on Expressed Sap pH, Organic Acid Synthesis, and Potassium Accumulation in Higher Plants. Plant Physiol. 1974 Jul;54(1):82–87. doi: 10.1104/pp.54.1.82. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Etherton B. Evidence for amino Acid-h co-transport in oat coleoptiles. Plant Physiol. 1978 Jun;61(6):933–937. doi: 10.1104/pp.61.6.933. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kirkby E. A., Mengel K. Ionic balance in different tissues of the tomato plant in relation to nitrate, urea, or ammonium nutrition. Plant Physiol. 1967 Jan;42(1):6–14. doi: 10.1104/pp.42.1.6. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sanz A., Ullrich C. I. Uptake of Acidic and Basic Sugar Derivatives in Lemna gibba G1. Plant Physiol. 1989 Aug;90(4):1532–1537. doi: 10.1104/pp.90.4.1532. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Stewart P. A. Modern quantitative acid-base chemistry. Can J Physiol Pharmacol. 1983 Dec;61(12):1444–1461. doi: 10.1139/y83-207. [DOI] [PubMed] [Google Scholar]