On the nature of humic substances Fedotov, G. N.; Shoba, S. A.
Eurasian soil science,
12/2015, Volume:
48, Issue:
12
Journal Article
Peer reviewed
It is argued that the isolation of low-molecular-weight compounds from humic substances does not prove their supramolecular nature, because small molecules can be sorbed on macromolecules by ...interacting with them due to noncovalent bonds. The relative mobility of molecular segments in humic substances has been proposed to be used as a criterion for the discrimination between the humic substances of supraand macromolecular nature. The macromolecules are characterized by mobility of their segments, whereas supramolecular systems have stiff structure. This difference between macroand supramolecules results in different behaviors of the matrices (gels) formed from them in the processes of segregation. In the macromolecules, the formations of a new phase appearing at the segregation (microphase separation) are of nano size, at least in one dimension. They are incapable of moving within the matrix and form a well-known, limited set of systems. In the supramolecular matrices, the new-phase formations should have higher mobility and ability to move within the matrix with the formation of particles and zones of not only nano, but also micro sizes, as well as a significantly larger set of systems, including fractal configurations. The experimental electron microscopic study of the humic matrices of soil gels shows that the new-phase formations in the matrix of humic substances have not only nano, but also micro sizes and are capable of moving within the matrix, which confirms the supramolecular nature of humic substances. The proposed method has allowed generalizing the supraand macromolecular approaches, because macromolecules can enter into the composition of supramolecular systems. It is no less important that the behavior of HSs can be perceived as the behavior of stiff impenetrable particles that may compose the structures of different types and sizes.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Granulodensimetric soil fractions isolated from chernozem, gray forest soil, and soddy-podzolic soil have been studied using a scanning electron microscope. The studies confirmed that the light ...fractions with density <1.8 g/cm³and particle size >53 μm mainly consists of plant residues; however, they also contain mineral particles covered with relatively thick organomineral films and carbonaceous substances. It has been shown that the clay fraction consists of a mixture of ultramicroaggregates of clay minerals ≤1 μm in size covered with a hydrophilic organomineral gel, and the organic matter of the residual fraction includes a stable highly aromatized (lignin-like) material, as well as coals and coal-like materials.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The effect of pre-sowing treatment of spring wheat seeds with suspensions of various actinomycete strains has been studied. It has been found that 4 out of 18 strains studied had a stimulating effect ...on seed germination in soils and plant development. The stimulation of seeds by these strains was not observed during seed germination in sand. It has been suggested that the mechanism of acceleration of seed development by actinomycetes could be based not only on the release of stimulating biologically active substances, but also on the consumption of allelotoxins by these microorganisms. The test carried out to study the possibility of actinomycete growth on a medium containing one of the most common allelotoxins, coumarin, has shown that actinomycetes promoting seed germination develop on this medium more intensively compared to strains that do not affect or inhibit the germination of spring wheat seeds. This confirms the proposed hypothesis that actinomycetes can stimulate seed germination through consumption of soil allelotoxins.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The influence of moisture and salinity of quartz sand on activation of the CO
2
emission and water consumption by seeds of spring wheat (
Triticum
), winter rye (
Secále cereále
), triticale ...(Triticosecale), and spring barley (
Hórdeum
) treated by a stimulant was studied under conditions of a model experiment. It was found that the seeds treated with a stimulant get advantages in the development upon a decrease in the water content of quartz sand. However, in the case of sand salinization, stimulant application did not lead to acceleration of seed development. The deficiency of moisture in saline sand also resulted in the increase of stimulant application efficiency. It was supposed that optimum moisture contents of quartz sand for seed germination and for the development of endophytic microorganisms do not coincide: active development of endophytic microorganisms stimulating seed development began under a lower moisture in comparison with that of the active seed development. Thus, active development of endophytic microorganisms upon the low moisture content mitigates the deceleration of seed development in the case of water deficiency. Hence, application of the microbial stimulant for seeds should be efficient in the cases, when germination of seeds proceeds under conditions of possible moisture deficiency, i.e., in the regions, where early spring droughts are frequent.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
As is well known from the mid-20th century, films of organomineral gels cover and bind soil particles in soils. Soil contact with water has been shown to lead to water absorption by gels and gel ...swelling. The change of gel properties in soils should manifest itself in a change in the viscosity of soil pastes. A vibrating viscometer was proposed to use to determine the viscosity of soil pastes. The physical meaning laid down in Einstein’s formula was used to interpret the results. This made it possible to assess the degree of gel swelling by the amount of water that remained capable of moving independently of soil particles, that is, was not included in soil gels (free water). The effect on the degree of swelling of soil gels was studied for (1) the moisture content in soil samples used to prepare soil pastes, (2) the time after adding water during the preparation of soil samples used subsequently to obtain soil pastes, and (3) the sample preparation of soil samples (initial, autoclaved, or dried to air-dry and absolutely dry states and re-moistened) used to obtain soil pastes. Experiments showed that (1) the degree of swelling of soil gels increased with the increasing moisture content in soil samples, (2) a longer time of interaction of soil samples with water led to a greater degree of swelling of soil gels, and (3) different degrees of swelling of soil gels were observed in pastes prepared from soil samples that had the same moisture content, but differed in sample preparation protocol.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
It is well-known that soil allelotoxicity and the water stability of soil structure are determined by the entry of plant residues into the soil, but the relationship of these soil properties has not ...been investigated. Soil samples from the fields of the Federal Research Center “Nemchinovka” after growing 25 cultivars of spring and winter wheat on plots with sod-podzolic soil are selected in this study. The effect of the soil’s allelotoxicity of plot samples on the germination of spring wheat seed of the Liza cultivar is studied by the biotesting method. The water stability of the soil structure is determined for the same samples. The existence of a sigmoid dependence between the allelotoxicity of soil samples and their water stability with a correlation greater than 95% is established. The presence of this dependence is apparently related to the increase in the soil’s water stability with an increase in the amount of fresh plant residues entering them, which is known from the literature, and the transition of the allelotoxins’ effects from stimulation to suppression with a growth in their concentration in soils.
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It is common knowledge that humic substances extracted from different sources are characterized by high biological activity (BA), though the nature of this phenomenon is not quite clear up to now. To ...expand our understanding of the BA of humic substances, we studied the effect of humates prepared from humic acids of different origin on the germination of seeds. The efficiencies of seed treatment by humate solutions obtained from preliminary purified humic acids extracted from peat, coal, and soil differed insignificantly. At the same time, the solutions of salts of humic substances obtained via alkaline extraction from peat without subsequent purification did not lead to statistically significant biological effects. The analysis of literature and our own data allowed us to conclude that the biological activity of humic acids could be related to their capacity to regulate the growth processes via binding growth inhibitors released into the solution upon seed swelling into the supramolecular complexes.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The effect of the introduction of a non-ionogenic surfactant Polysorbate 20 into a sorption preparation (CB-H-BYA) on the structure of sorbent layers formed on the surface of spring wheat seeds ...during their pre-sowing treatment has been studied using electron microscopy. According to the results, an increase in the efficiency of sorption preparations containing Polysorbate 20 is based on an intensification of the bentonite aggregate disintegration into individual montmorillonite particles and a formation of more dense protective sorption layer providing a better protection of seeds against allelotoxins on the seed surface. The introduction of non-ionogenic surfactants into the preparation increases a sorption capacity of a bentonite–humus complex that results in a decreased gibberellin activity in a solution. Therefore, to achieve the maximum physiological activity of gibberellin in a preparation solution, it is necessary to increase its concentration from 100 to 300 mg/L. As a result, the stimulating effect increases from 36 to 55%.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
39.
Plant Stress and Allelotoxicity of Soils Sandukhadze, B. I.; Fedotov, G. N.; Davydova, N. V. ...
Doklady. Biological sciences,
08/2022, Volume:
505, Issue:
1
Journal Article
Peer reviewed
Stress exposures during vegetation are known to reduce the yield in crops, but the intensity and duration of stress is rather difficult to determine from the crop loss. Allelotoxins are released from ...plants into soil on exposure to stress factors. Soil allelotoxicity after vegetation was assumed to provide a diagnostic parameter that characterizes the total stress effect on crops. To verify the assumption, changes in soil allelotoxicity were studied after vegetation of three winter wheat cultivars fed with different amounts of nitrogen fertilizers. The cultivars Nemchinovskaya 85, Moskovskaya 39, and Lutescens 982/08 were found to differently respond to fertilizing. Nemchinovskaya 85 and Lutescens 982/08 showed lower stress responses at higher doses of nitrogen fertilizers, while their responses were appreciable when soil nitrogen was lacking. In the case of Moskovskaya 39, higher doses of nitrogen fertilizers caused an adverse reaction of increased allelotoxin release. Stepwise nitrogen fertilization was concluded to be necessary for preventing delayed plant development in the case of this cultivar. The results confirmed that soil allelotoxicity measured growing plants can serve as an indicator of stress caused by the growth conditions and use of various agricultural techniques.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The structural organization of the organic matrix of humic substances in soils has been analyzed, and the conclusion has been drawn that the existence of humic matrix is determined by contacts ...between the hydrophilic sites of humic particles in dry soils and between their hydrophobic sites in wet soils. It follows from the advanced supposition that the wetting–drying process should cause a structural transition (reorganization of the humic matrix), which should affect the properties of soils. To verify this supposition, the effect of soil moisture on the electrical resistivity of soil–water extracts, suspensions, and pastes has been studied. It follows from the studies performed that soil electrolytes are fixed in dry soils during drying and are gradually released into solution. However, beginning from a specific soil water content, the release of electrolytes occurs almost immediately after their contact with water. The obtained data suggest that an energy barrier should be overcome for the release of electrolytes from the soils with water content below the specific limit. There is no energy barrier for the soils with water content higher than this limit. The existence of structural transition in the humic matrix of soil gels well explains these results. The effect of energetic impacts on the structural transition has been studied. It has been shown that the study of structural transition should avoid operations that increase the number and amplitude of energy fluctuations in the systems.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
