Interannual Variation of Stomatal Traits Impacts the Environmental Responses of Apple Trees

Stomata are fundamental to plant-water relations and represent promising targets to enhance crop water-use efficiency and climate resilience. Here, we investigated stomatal density (SD) variation in 269 apple accessions across 3 years (2019-2021), which demonstrated significant differences between accessions but consistency over time. We selected 2 subsets of 20 accessions, each with contrasting SD: high stomatal density (HSD; 370-500 mm ) and low stomatal density (LSD; 192-316 mm ). SD groups were compared in stomatal function, leaf physiology and crop productivity across two seasons (2021-2022). LSD had lower stomatal conductance (g ) and higher intrinsic water-use efficiency in both years (p