Bioregulators are natural chemical compositions that induce biological responses in plant
tissues. Screening of bioactive compounds showed that the wide range of natural products
might contain constituents – potential regulators of physiological processes in a plant, namely
whole or selective extracts from medicinal and weed plants, seaweeds, microorganisms,
insects, shale ore, and bituminous rocks. The large diversity of natural regulators is
predetermined by wide chemical classes that possess biological activity. Protein hydrolysates
(peptides, polypeptides, amino acids), polysaccharides, polyphenols, terpenoids, steroids,
saponins, vitamins, phytohormone-like substances, volatile oils, microelements were tested as
growth regulators, immunomodulators, antioxidants, and biostimulants. Biologically active
substances synthesized by higher plants during secondary metabolism perform important
regulatory functions in the plant cells and are able, even in nano amounts, to normalize many
vital processes.
This review focuses on plant secondary metabolites, which are considered bioregulators,
their biological effects, and possible mechanism of action. Special attention was paid to steroid,
iridoid, and flavonoid glycosides, practices for their obtaining and application. Recent studies
carried out in laboratories, greenhouses and open field experiments demonstrated that
applications of bioregulators increase the seeds germination, growth of root and seedlings,
plants development, rise yield, and nutritive value of crops. Many studies reported positive
effects of bioregulators on the growth and yield increasing of cereal and vegetable crops
through seeds pre-sowing treatment. To noted, that after the application of bioregulators the
market quality of crops, biochemical compositions, and nutritive value of tomatoes, onions,
white cabbage, and carrot were also positive changed. Moreover, seeds treatment with
bioregulators reduced biotic and abiotic stresses. Thus, corn seeds preliminary treated with
bioregulators and subjected to moderate thermal stress, retained their germination capacity,
while untreated seeds were injured by temperatures.
Diverse effects of bioregulators are elicited depending on the times and mode of their
application, concentrations, species, and state of plants and environmental conditions. For
example, iridoid and flavonoid glycosides acted variety-specific inside the same plant species.
Modern analysis of the microarray data showed that the treatment with bioregulators is able
to modulate the expression level of about 4,000 genes in tomatoes plant, which is involved in
several biological processes like stress responses, protein, and secondary metabolism
transport, and antioxidant defense. However, the molecular mechanisms of their effects remain
to be fully elucidated. In conclusion, since bioregulators are multifunctional and numerous, a
comprehensive preliminary study is necessary for the correct choice of product.