Temporal control of root system architecture under osmotic stress: ABA–SnRK2 signaling and adaptive plasticity

Drought and salt stress impose osmotic and ionic challenges on plant roots, with drought reducing soil water potential and salt imposing additional ionic toxicity beyond osmotic stress, driving the plastic remodeling of root system architecture (RSA). Abscisic acid (ABA) is a central hormone regulating root adaptability, and its signaling coordinates adaptive responses of roots across multiple time scales through the SNF1-related protein kinase 2 (SnRK2) family kinases. This review systematically summarizes the temporal coding mechanisms of the ABA-SnRK2 signaling network underlying root adaptation to osmotic stress. We propose that plant roots achieve a dynamic balance between short-term defense and long-term adaptation through the coordinated activities of different SnRK2 subgroups along the temporal axis. This proposed "balance point" of temporal coding is shaped by multiple temporal readouts. We also review how crosstalk between ABA and other hormones such as auxin fine-tunes root plasticity. Based on this framework, we propose a "balance point engineering" strategy that provides a theoretical blueprint for designing stress-tolerant crops with tunable durations of stress responses.