On the Relation Between the Effects of Auxin on Growth, pH and Potassium Transport |
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Authors: | I. ILAN S. SHAPIRA |
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Affiliation: | Tel Aviv University, Department of Botany, The Dr. George S. Wise Center for Life Sciences, Tel Aviv, Israel |
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Abstract: | The relation between the effects of auxin on growth, pH and potassium transport in hypocotyl segments of Helianthus annuus was studied. In a solution containing 20 mM Na2SO4 auxin-induced growth was accompanied by an auxin-induced pH drop in the medium. (NH4)2SO4, at the same concentration, brought about an almost complete abolishment of the effect of auxin on the pH. The magnitude of auxin-induced growth was, however, only slightly reduced. This result does not confirm the hypothesis according to which the action of auxin on growth is a result of its effect on the pH. In a solution containing 2 mM sodium phosphate buffer an inhibitory action of IAA on the release of potassium from the tissue was observed. Addition of 20 mM Na2SO4 to the medium brought about a complete abolishment of this effect. The magnitude of auxin induced pH drop was, however, similar in the two treatments. It was concluded that, although under suitable experimental conditions, a close relationship may exist between the effects of auxin on pH on K+ transport, the coupling between the two phenomena is not obligatory. |
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