A study of the organic and amino acids in cotton roots during ion uptake

Abstract

The effect of various inorganic salts on the organic and amino acid concentrations during ion uptake was studied in the roots of cotton (Gossypium hirsutum L. var. Acala 442). Gas chromatography and liquid-liquid column chromatography were used to identify and quantitize the various organic and amino acids respectively. Development to at least 6 days of age was required before young cotton roots would start to accumulate K+ from K₂SO₄ solutions in the concentration range corresponding to mechanism I. The malic acid content increased in response to increased K+. In the excised roots, the K+ increase was less than in the intact plants and the malic acid increase appeared to be due to CO² fixation resulting in an increase in total acidity as measured by organic acid concentrations. The malic acid increase in the roots of intact cotton plants was due not only to CO² fixation but also to a conversion of tartaric acid to malic acid. When K₂SO₄ was used at 10�² M, well within the high concentration mechanism, the K+ increases were linear indicating diffusive permeation. The organic acid increase due to K+ accumulation from 10�² M K₂SO₄ was not as great as that due to K+ accumulation from 10�� M K₂SO₄. Thus the conclusion was drawn that organic acid changes are related to mechanism I, the low concentration mechanism. When Na+ was used as the test ion, citric acid increased. The hypothesis is advanced that the cation-organic acid affinity is different for each cation and organic acid..