Rui, M.Chen, R.Jing, Y.Wu, F.Chen, Z.H.Tissue, D.Jiang, H.Wang, Y.2025-09-182025-09-182024New Phytologist, 2024; 242(6):2479-24940028-646X1469-8137https://hdl.handle.net/2440/147419Climate change-induced drought is a major threat to agriculture. C₄ crops have a higher water use efficiency (WUE) and better adaptability to drought than C₃ crops due to their smaller stomatal morphology and faster response. However, our understanding of stomatal behaviours in both C₃ and C₄ Poaceae crops is limited by knowledge gaps in physical traits of guard cell (GC) and subsidiary cell (SC). We employed infrared gas exchange analysis and a stomatal assay to explore the relationship between GC/SC sizes and stomatal kinetics across diverse drought conditions in two C₃ (wheat and barley) and three C₄ (maize, sorghum and foxtail millet) upland Poaceae crops. Through statistical analyses, we proposed a GCSC-τ model to demonstrate how morphological differences affect stomatal kinetics in C₄ Poaceae crops. Our findings reveal that morphological variations specifically correlate with stomatal kinetics in C₄ Poaceae crops, but not in C₃ ones. Subsequent modelling and experimental validation provide further evidence that GC/SC sizes significantly impact stomatal kinetics, which affects stomatal responses to different drought conditions and thereby WUE in C₄ Poaceae crops. These findings emphasize the crucial advantage of GC/SC morphological characteristics and stomatal kinetics for the drought adaptability of C₄ Poaceae crops, highlighting their potential as future climate-resilient crops.en© 2024 The Authors, © 2024 New Phytologist Foundation.C3 and C4 crops; drought; stomatal development; stomatal kinetics; stomatal morphology; water use efficiency.Crops, AgriculturalWaterAdaptation, PhysiologicalCell SizeKineticsModels, BiologicalPlant StomataDroughtsEdible GrainJournal article10.1111/nph.19757738304Chen, Z.H. [0000-0002-7531-320X]