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Agronomy Journal Abstract -

Relationship of pH to Ion Uptake Imbalance by Varieties of Wheat (Triticum vulgare)1


This article in AJ

  1. Vol. 64 No. 4, p. 476-481
    Received: Oct 28, 1971

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  1. C. S. Dodge and
  2. A. J. Hiatt2



Varietal differences in plant-induced pH changes have been considered a possible factor in Al tolerance. The objective of this study was to determine the magnitude of plant-induced pH changes by wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) and to determine the cause of observed varietal differences. Varieties of wheat or barley differed considerably in their effect on the pH Level of complete nutrient solutions. Ion uptake and H+ transfer between plants of three varieties of wheat and KNO3-Ca(NO3)2 solutions were measured to determine the reason for varietal differences in plant-induced pH shifts. Changes in nutrient solution pH were attributable to differences in anion and cation absorption. Consequently, varietal differences in effect on solution pH levels were accounted for by varietal differences in anionminus-cation uptake (A-C) values.

Nutrient solutions from which anions had been absorbed in excess of cations were highly buffered. This buffering capacity was lost when the solutions were acidified and aerated, suggesting that HCO-3 exchanged for the excess anions.

Plant-induced changes in nutrient solution pH varied with the form of N in the solution. When NO3- was the only form of N present, pH levels consistently increased from the initial level. However, solution pH decreased when NH4+ was present in quantities as low as 0.5% of the total N.

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