Abstract
Abstract The effect of different salts and inhibitors on the root pressure of Zea mays.— The influence of various salt solutions and inhibitors on the exudation rate has been investigated with young excised primary roots of Zea mays. The following results were obtained. — The effect of chlorides on the exudation rate was higher than the effect of sulphates K+ and Na+ effected higher flux rates than Ca2+ and Mg2+ The highest exudation rate was obtained with KCl. — In comparison to an isotonic Lutrol‐solution (a liquid condensed polyethylenoxid) a 0.5525 molar KCl‐solution, applicated on the root stump, increased the exudation rate considerably. — Metabolic inhibitors and anaerobic conditions decreased the exudation rate. — Experiments, concerning the influence of metabolic inhibitors on the exudation and on the Rb‐uptake showed a highly significant positive correlation (r =+0.72***) between the exudation rates and the Rb‐concentrations in the exudates. The Rb‐accumulation in the root tissue was not correlated to the exudation rate. — The experimental data agree with the concept of a transversal water transport in the root tissue, effected by osmotic forces. The root pressure is based on the osmotic gradient between the xylem sap and the outer solution. This gradient is built up by the metabolic secretion of ions into the xylem sap. It is supposed that the transversal water transport in the roots mainly goes through the free space of the cortex.
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