Stage-specific drought alters stem hormones and non-structural carbohydrate metabolism to sustain the yield of drip-irrigated spring wheat in arid regions

Frequent and severe drought events strongly threaten plant survival. Non-structural carbohydrates (NSC) act as essential “buffers” for maintaining plant function under drought conditions. Therefore, understanding NSC metabolic patterns in wheat stems and clarifying how drought influences NSC metabolism are crucial for improving yield stability and stress tolerance. In this study, two spring wheat cultivars [Xinchun 6 (XC 6, drought-tolerant) and Xinchun 22 (XC 22, drought-sensitive)] were subjected to two-year field experiments under normal irrigation (75–80% field capacity, CK), 7-day mild drought (60–65% FC; T1 at tillering and J1 at jointing), and 7-day moderate drought (45–50% FC; T2 at tillering and J2 at jointing), resulting in a total of 10 treatment combinations. We investigated the effects of drought on stem hormone content, NSC related enzyme activity, NSC accumulation and reactivation, and grain yield. The results showed that hormone contents, NSC enzyme activities, NSC accumulation and remobilization, and yield across internodes were most favorable under T1, with the other internodes exhibiting the best performance. Compared with CK, these physiological changes were associated with 1.03–17.43% higher grain yield. Correlation analysis and variable importance in projection (VIP) scores further indicated that stem dry matter (SDM), indole-3-acetic acid (IAA), and sucrose phosphate synthase (SPS) made the greatest contributions to yield. In conclusion, maintaining 7-day mild drought (60–65% FC) at the tillering can promote hormonal balance, enhance NSC metabolism, and stabilize yield, which can serve as an effective water management strategy for the sustainable production of spring wheat under drip irrigation in arid regions. • 7-day mild drought at tillering enhances stem hormone balance and carbon metabolism. • 7-day mild drought at tillering promotes carbohydrate remobilization and maintains yield stability. • Stem dry matter, indole-3-acetic acid, and sucrose phosphate synthase drive wheat yield.