Letter | Published:

Auxin, carbon dioxide and hydrogen ions

Naturevolume 257page68 (1975) | Download Citation



HYDROGEN ions can partially mimic the effect of indoleacetic acid (IAA) on plant cell elongation1. This observation has been elaborated in a proposal that the initial action of IAA causes the activation of a proton pump at the cell membrane. The pumping of protons would cause a lowering of the pH at the cell wall, leading to wall loosening2. This proposal has been supported in studies in which the pH of the medium surrounding oat coleoptile3–5 or etiolated pea stem6 sections was observed to drop when auxin was applied. This acidification was most pronounced when tissue sections were used from which the epidermis with the cuticle had been peeled off3, and was presumed to be caused by the proton pump activated by IAA.

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    Bonner, J., Protoplasma, 21, 406–423 (1934).

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    Hager, A., Henzel, H., and Krauss, A., Planta, Berl., 100, 47–75 (1971).

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    Rayle, D., Planta, Berl., 114, 63–73 (1973).

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    Cleland, R., Proc. natn. Acad. Sci. U.S.A., 70, 3092–3093 (1973).

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    Johnson, K., Daniels, D., Dowler, M., and Rayle, D., Pl. Physiol., Lancaster, 53, 224–228 (1974).

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    Marre, E., Lado, P., Caldogno, R., and Colombo, R., Pl. Sci. Lett., 1, 179–184 (1973).

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    Bonner, J., J. gen. Physiol., 17, 63–80 (1933).

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    Margolis, E. J., Chemical Principles of Ionic Equilibria (Macmillan, New York, 1966).

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    Evans, M., Ray, P. M., Reinhold, L., Pl. Physiol., Lancaster, 47, 335–341 (1971).

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    Martin, J., and Juniper, B., The Cuticles of Plants (St Martin's Press, New York, 1970).

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  1. Joint Science Department, The Claremont Colleges, Claremont, California, 91711

    •  & D. SADAVA


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