SIGNIFICANCE AND APPLICATION OF PLANT GROWTH REGULATORS

Abstract

Plant growth regulators (PGRs) are natural or synthetic compounds that modulate plant growth, development, and stress responses by adjusting endogenous hormone concentrations and influencing signaling pathways. This review examines the roles of key phytohormones which regulate physiological processes and tolerance mechanisms to abiotic stress. Abscisic acid emerges as the principal stress-responsive hormone, governing stomatal closure, water balance maintenance, and osmotic adjustment under adverse conditions. Auxins regulate cell elongation, vascular differentiation, and root architecture, with their homeostasis being significantly altered under environmental stress. Cytokinins promote photosynthetic efficiency and delay senescence, while gibberellins control stem elongation, seed germination, and flowering induction. Jasmonates contribute to both biotic and abiotic stress defense through activation of antioxidant systems and stomatal regulation. The review also examines how humic substances function helping plants better tolerate stress by improving nutrient absorption, activating antioxidant systems, and influencing auxin-like activity. Humic acids interact with root cells, influence ion absorption, and mitigate oxidative damage caused by reactive oxygen species under stress conditions. Practical applications of PGRs in agriculture are discussed, including their use in promoting flowering, fruit development, vegetative propagation, and yield enhancement. The integration of PGRs with biostimulants and microbial inoculants represents a promising strategy for sustainable crop production under increasingly challenging environmental conditions. Future research directions emphasize molecular approaches for optimizing hormonal manipulation and developing stress-resilient crop varieties.

Key words: рlants, growth regulators, phytohormones, humic substances.