Abstract: Drought is one of the major abiotic stresses that limits plant growth. Roots, the primary organs responsible for water uptake, are the first to perceive and respond to water deficit conditions. Therefore, maintaining activity and promoting primary root elongation under drought stress are considered critical adaptive strategies for drought survival. However, despite increasing evidence of primary root elongation under drought stress, the underlying mechanisms, particularly hormonal regulation and its integration with environmental cues, remain poorly understood across different species and developmental contexts. Previous studies have shown that a highly coordinated network of plant hormone crosstalk plays a significant role in this adaptive process. In this review, data from diverse plant species confirmed the promoting effect of drought on primary root growth. This study further elucidated the role of abscisic acid (ABA) in enhancing primary root growth under drought conditions and explored the potential coordination of ABA with other hormones, including ethylene, auxin, and cytokinin, to synergistically promote primary root elongation. Furthermore, several physiological processes, such as cell cycle regulation, osmotic adjustment, and lateral root growth dynamics, had been systematically investigated for their contributions to this adaptive response. By dissecting these mechanisms, this study aims to propose feasible strategies to increase plant drought tolerance through targeted root system architecture modification, addressing challenges posed by future climate scenarios.

Key words: drought stress, primary root growth, ABA, plant hormones, drought tolerance