Abstract
The uptake of auxin by 1-mm slices of corn (Zea mays L.) coleoptiles, a tissue known to transport auxin polarly, depends on the pH of the medium. Short-term uptake of indole-3-acetic acid (IAA) in coleoptiles increases with decreasing pH of the buffer as would be expected if the undissociated weak acid, IAA·H, were more permeable than the auxin anion, IAA-, and IAA- accumulates in the tissues because of the higher pH of the cytoplasm. Although uptake of [3H]IAA is reduced in neutral buffers, it is greater than expected if it were limited to just the extracellular space of the tissue. The radioactivity accumulated by the tissue can be quantitatively extracted by organic solvents and identified as IAA by thin-layer chromatography. The tissue radioactivity is freely mobile and can efflux from the tissue. Thus these cells in pH 5 buffer are able to retain an average internal concentration of mobile IAA that is at least several times greater than the external concentration. A prominent feature of auxin uptake from acidic buffers is enhanced accumulation at high auxin concentration. This indicates that, in addition to fluxes of IAA·H, a saturable site is involved in auxin uptake. Whenever the auxin-anion gradient is directed outward, saturating the efflux of auxin anions increases accumulation. Furthermore, the observed slowing of short-term uptake of radioactive IAA by increasing concentrations of IAA or K+ indicates either an activation of the presumptive auxin leak or saturation of another carrier-mediated uptake system such as a symport of auxin anions with protons. By contrast in neutral buffers, effects of concentration on uptake rates disappear. This implies that at neutral pH the anion leak is decreased and influx depends on the symport.
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References
Cleland, R.E.: The dosage-response curve for auxin-induced cell elongation: a reevaluation. Planta 104, 1–9 (1972)
Cleland, R.E.: Kinetics of hormone-induced H+ excretion. Plant Physiol. 58, 210–213 (1976)
Cleland, R.E., Prins, H.B.A., Harper, J.R., Higinbotham, N.: Rapid hormone-induced hyperpolarization of the oat coleoptile transmembrane potential. Plant Physiol. 59, 395–397 (1977)
Collander, R.: Cell membranes: their resistance to penetration and their capacity for transport. In: Plant Physiology, A Treatise, vol. II, pp. 3–102, Steward, F.C., ed. New York: Academic Press 1959
Dainty, J.: Water relations of plant cells. In: Encyclopedia of Plant Physiology, N.S., vol. 2, Transport IIA: Cells, pp. 12–35, Lüttge, U., Pitman, M.G., eds., Berlin, Heidelberg, New York: Springer 1976
Davies, D.D.: Control of an by pH. Symp. Soc. Exp. Biol. 27, 513–529 (1973)
Davies, P.J., Rubery, P.H.: Components of auxin transport in stem segments of Pisum satium L. Planta 142, 211–219 (1978)
Dohrmann, U., Hertel, R., Kowalik, H.: Properties of auxin binding sites in different subcellular fractions from maize coleoptiles. Planta 104, 97–106 (1978)
de la Fuente, R.K., Leopold, A.C.: Kinetics of polar auxin transport. Plant Physiol. 41, 1481–1484 (1966)
Evans, M.L., Ray, P.M.: Timing of the auxin response in coleoptiles and its implication regarding auxin action. J. Gen. Physiol. 53, 1–20 (1969)
Goldsmith, M.H.M.: The transport of auxin. Ann. Rev. Plant Physiol. 19, 347–360 (1968)
Goldsmith, M.H.M.: The polar transport of auxin. Ann. Rev. Plant Physiol. 28, 439–478 (1977)
Goldsmith, M.H.M., Cataldo, D.A., Karn, J., Brenneman, T., Trip, P.: The rapid nonpolar transport of auxin in the phloem of intact Coleus plants. Planta 116, 301–317 (1974)
Jacobs, M., Hertel, R.: Auxin binding to subcellular fractions from Cucurbita hypocotyls: in vitro evidence for an auxin transport carrier. Planta 142, 1–10 (1978)
Jacobs, M., Ray, P.M.: Rapid auxin-induced decrease in free space pH and its relationship to auxin-induced growth in maize and pea. Plant Physiol. 58, 203–209 (1976)
Leopold, A.C., Hall, O.F.: Mathematical model of polar auxin transport. Plant Physiol. 41, 1476–1480 (1966)
MacRobbie, E.A.C., Dainty, J.: Sodium and potassium distribution and transport in the seaweed Rhodymenia palmata (L.) Grev. Physiol. Plant. 11, 782–801 (1958)
Osborne, D.J., Mullins, M.G.: Auxin, ethylene and kinetin in a carrier-protein model system for the polar transport of auxins in petiole segments of Phaseolus vulgaris. New Phytol 68, 977–991 (1969)
Pfrüner, H., Bentrup, F.W.: Fluxes and compartmentation of K+, Na+ and Cl-, and action of auxins in suspension-cultured Petroselinum cells. Planta 143, 213–223 (1978)
Raven, J.A.: Transport of indoleacetic acid in plant cells in relation to pH and electrical potential gradients, and its significance for polar IAA transport. New Phytol. 74, 163–172 (1975)
Ray, P.M.: Auxin-binding sites of maize coleoptiles are localized on membranes of the endoplasmic reticulum. Plant Physiol. 59, 594–599 (1977)
Ray, P.M., Dohrmann, U., Hertel, R.: Characterization of naphthaleneacetic acid binding to receptor sites on cellular membranes of maize coleoptile tissue. Plant Physiol. 59, 357–364 (1977a)
Ray, P.M., Dohrmann, U., Hertel, R.: Specificity of auxin binding sites on maize coleoptile membranes as possible receptor sites for auxin action. Plant Physiol. 60, 585–591 (1977b)
Rubery, P.H.: The specificity of carrier-mediated auxin transport by suspension cultured crown-gall cells. Planta 135, 275–283 (1977)
Rubery, P.H.: Hydrogen ion dependence of carrier-mediated auxin uptake by suspension-cultured crown-gall cells. Planta 142, 203–206 (1978)
Rubery, P.H., Sheldrake, A.R.: Effect of pH and surface charge on cell uptake of auxin. Nature (London) New Biol. 244, 285–288 (1973)
Rubery, P.H., Sheldrake, A.R.: Carrier-mediated auxin transport. Planta 118, 101–121 (1974)
Stahl, E.: Thin-layer chromatography. New York: Academic Press 1965
Zenk, M.H.: Isolation, biosynthesis, and function of indoleacetic acid conjugates, In: Regulateurs Naturels de la Croissance Végétale (Coll. Int. CNRS No. 123), pp. 241–249 Paris: CNRS 1953
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Edwards, K.L., Goldsmith, M.H.M. pH-Dependent accumulation of indoleacetic acid by corn coleoptile sections. Planta 147, 457–466 (1980). https://doi.org/10.1007/BF00380188
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DOI: https://doi.org/10.1007/BF00380188