Factors affecting potassium uptake and loss by Beech mycorrhiza

Edmonds, A.S.; Wilson, J.M.; Harley, J.L.

New Phytologist 76(2): 307-315

1976


ISSN/ISBN: 0028-646X
DOI: 10.1111/j.1469-8137.1976.tb01466.x
Accession: 000375220

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Abstract
Describes experiments to examine the possibility that earlier estimates [cf. FA 22, 252] of K uptake by excised mycorrhizae of F. sylvatica from solutions of monovalent ions, and of losses of K at temperatures > 20 deg C, might be artefacts due to the absence of Ca. The effects of carbohydrate supply on loss of K, and the extent to which excessive osmotic pressure of the solutions might increase the loss of K, were also investigated. Results showed that maximum K uptake was achieved by Beech mycorrhizae from concentrations of chloride of ca. 0.2 mM. The addition of NaCl (up to 0.5 mM) did not significantly reduce K uptake from 0.1 mM chloride solutions, though the KCl significantly reduced Na uptake. K was rapidly lost from mycorrhizal tissues at temperatures > 20 deg C, but only after some delay from tissues at lower temperatures. The addition of Ca ions ( not more than 1.0 mM CaCl2) did not significantly affect the uptake or loss of K. CaCl2 added to RbCl solutions slightly reduced the uptake of Rb. Losses of K from mycorrhizal tissues at temperatures > 20 deg may be prevented by the application of glucose or fructose. Neither the process of carbohydrate uptake nor the increased internal concentration of carbohydrate itself is responsible for the reduction in loss of K. It seems probable that factors bringing about the retention of K are generated in carbohydrate metabolism. The loss of K engendered by high osmotic pressure of the external solution seems to be a separate phenomenon from that which occurs at high temperatures. Max. K uptake is achieved by beech mycorrhizas from concs. of chloride of c. 0.2 mM. Addition of NaCl up to 0.5 mM does not significantly reduce K+ uptake from 0.1 mM chloride sols. although the KCl significantly reduces Na+ uptake. K is rapidly lost from mycorrhizal tissues at temps. above 20 deg C, but only after some delay from tissues at lower temps. Addition of Ca ions (up to 1 mM CaCl2) does not significantly affect K uptake or loss. CaCl2 added to RbCl sols. slightly reduces Rb+ uptake. Losses of K+ from mycorrhizal tissues at >20 deg may be prevented by the application of glucose or fructose. Neither the process of carbohydrate uptake nor the increased internal carbohydrate conc. itself is responsible for the reduction in K loss. It seems probable that factors bringing about the retention of K are generated in carbohydrate metabolism. The K loss engendered by high osmotic pressure of the external sol. seems to be a separate phenomenon from that which occurs at high temps. Max. K uptake is achieved by beech mycorrhizas from concs. of chloride of c. 0.2 mM. Addition of NaCl up to 0.5 mM does not significantly reduce K+ uptake from 0.1 mM chloride sols. although the KCl significantly reduces Na+ uptake. K is rapidly lost from mycorrhizal tissues at temps. above 20 deg C, but only after some delay from tissues at lower temps. Addition of Ca ions (up to 1 mM CaCl2) does not significantly affect K uptake or loss. CaCl2 added to RbCl sols. slightly reduces Rb+ uptake. Losses of K+ from mycorrhizal tissues at >20 deg may be prevented by the application of glucose or fructose. Neither the process of carbohydrate uptake nor the increased internal carbohydrate conc. itself is responsible for the reduction in K loss. It seems probable that factors bringing about the retention of K are generated in carbohydrate metabolism. The K loss engendered by high osmotic pressure of the external sol. seems to be a separate phenomenon from that which occurs at high temps.

Factors affecting potassium uptake and loss by Beech mycorrhiza