Аннотация:A comparative evaluation of the mitigating activity of humic substances (HS) derived
from coal and peat towards the seedlings of wheat Triticum aestivum L. under water
deficiency conditions has been performed. The studied HS included humic (HA), fulvic
acids (FA) and hymatomelanic acid (HMA) isolated from coal and peat as they are the
main sources for industrial humates designed for use in agriculture as plant growth
regulators. All the studied HS were characterized by the methods of elemental analysis,
size-exclusion chromatography and 13C NMR spectroscopy.
Bioassay experiments was performed according to [1]. To create water deficiency,
the hyperosmotic solution of polyethylene glycol with a molecular weight of 6,000 D
(PEG 6000) with concentration 100 g/l (osmotic pressure –0.15 MPa) was used.
Evaluation of the protective effect of HS was carried out at constant concentration of PEG-
6000 and concentrations of HS varying in the range 5–100 mg/L. Distilled water was used
as a blank solution. Wheat seeds were placed in the Petri dishes containing solutions
under study and left in the dark at 24C for 72 h. Then the length of roots and shoots of
wheat seedlings was measured. Protective effect of HS was assessed based on
comparison the lengths of roots and shoots of seedlings in the tested solutions to the blank
one.
Experiments demonstrated that HS were able to reduce partially the inhibition of
wheat seedlings’ growth under water deficit caused by hyperosmotic solution of PEG-
6000. The protective effect of HS was revealed to enhance along with increasing the
content of oxygen-substituted aromatic fragments in HS structure. Thus, the obtained
results allow suggesting about increasing the protective effect of HS in relation to plants
under conditions of water deficit by increasing the content of phenolic fragments. The
observed mitigating activity of HS could not be explained by their binding with PEG-6000,
which is a negatively charged polyelectrolyte. Therefore, HS possess the ability to reduce
the negative effects of water deficiency due to their direct effect on plants. As mitigating
activity of HS enhanced by increasing the content of phenolic fragments that may indicate
the antioxidant activity of HS as the main mechanism of their protective activity under
conditions of water deficit. However, to confirm this assumptions, an additional research
aimed at the study of membranotropic properties of humic materials should be conducted.
References
1. Klein O.I., Kulikova N.A., Konstantinov A.I., Fedorova T.V. et al. // Appl. Biochem.
Microbiol. 2013. 49(3):287–295.
This research was performed in the framework of state assignment (CITIS
#116020110002-8).