The plasticity of crop development is crucial for survival and yield stability under adverse conditions. Saline-alkaline soil is a major environmental constraint limiting wheat productivity. Elucidating the regulatory basis of wheat developmental plasticity under salt stress is crucial for improving salt tolerance and yield stability. In this study, salt stress promotes the initiation of lateral root (LR) primordia while inhibiting LR emergence in wheat. Upon return to non-stress conditions, these primordia rapidly develop into LRs, enabling swift recovery and root system expansion. We identify glycogen synthase kinase 3 (TaGSK3) as a molecular switch that regulates this plastic response via brassinosteroid and auxin signaling pathways. By this mechanism, environmental signals are transduced into root development plasticity via TaGSK3 phosphorylation. This work provides new insights into how crops control developmental plasticity under stress.