Contribution of organic acids to the acidification of the rhizosphere of maize seedlings |
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Authors: | Wolfgang Petersen Michael Böttger |
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Institution: | (1) Institut für Allgemeine Botanik, Ohnhorststr. 18, D-2000 Hamburg 52, Germany |
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Abstract: | The participation of organic acids in the process of soil acidification was related to other H+ pumping processes. The ratio between efflux of organic acids and proton secretion of maize roots was determined with the
use of a pH-stat combined with a collecting system for organic acids. Changes in the composition of carboxylic acids influenced
by nitrogen supply were monitored by HPLC and via enzymatic conversion. The following substances were found to be secreted
by maize roots: glycolate, glyoxylate, fumarate, 2-oxoglutarate and oxalate. Malate, however, could not be detected.
There is no organic acid dominantly secreted by the roots, but changes are observed during aging which might result from deficiencies
of nutrients e.g. P.
Fertilization of N-deficient plants with urea leads to a significant change in the composition of acids secreted. In this
case, oxalate was additionally detected with a concomitant increase in glyoxylate, indicating important changes in metabolism.
Acidification of the rhizosphere is predominantly maintained by secretion of protons, not by efflux of organic acids, which
contributed 0.2 to 0.3% to this process only. The role of organic acids in nutrient uptake is discussed. |
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Keywords: | enzymatical conversion organic-acid secretion proton secretion rhizosphere roots Zea mays |
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