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The Effect of Low Concentrations of Stable Electrophoretic Fractions of Soil Humic Acids on Stimulation/Inhibition of the Root Length of Radish Seedlings


By combining low-pressure size-exclusion chromatography with analytical polyacrylamide gel electrophoresis, three stable electrophoretic fractions A, B, and C + D were isolated from soil humic acids (HAs) of chernozem and IHSS standard HA 1S102H. The fractions differ in electrophoretic mobility and molecular size (MS); MSA > MSB > MSC + D. The initial HAs and their fractions are assayed for their biological activity (the ability to stimulate or inhibit the growth of primary roots of 3-day-old radish seedlings) at concentrations of 1, 10–3, and 10–4 mg/L. A statistically significant stimulatory effect (p < 0.05) is observed for both HAs and their fractions A and B (with largest MSs) at an ultralow concentration of 10–3 mg/L. At this concentration, the fraction C + D (with smallest MS) from both HA preparations inhibits the germination of radish seeds. Analysis of the structural characteristics suggests that the main factor determining the growth stimulation is the presence of aliphatic components in HAs and their fractions rather than their MS, whereas their aromatic components inhibit the plant growth.

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The work was supported by the Russian Foundation for Basic Research (projects nos. 18-016-00078a and 19-05-00056a) and budget funding.

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Correspondence to O. A. Trubetskoi.

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Translated by G. Chirikova

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Trubetskaya, O.E., Trubetskoi, O.A. The Effect of Low Concentrations of Stable Electrophoretic Fractions of Soil Humic Acids on Stimulation/Inhibition of the Root Length of Radish Seedlings. Eurasian Soil Sc. 54, 1089–1096 (2021).

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  • humic substances
  • fractionation of humic acids
  • electrophoresis
  • size-exclusion chromatography