Exploring edamame survival mechanisms under combined drought and heat stress: Photosynthesis efficiency and carbohydrate accumulation

•Different cultivars exhibit different tolerate combined drought and heat (DH) stress:.•The DH stress reduced photochemical reactions and carbohydrate accumulation in UVE17.•AGS429 preserved the light-harvesting pigments, optimised the photochemical reactions and reduced stomatal closure during flowering, thereby facilitating greater energy production needed for seed production.•AGS429 and UVE14 had increased trehalose, suggesting high osmotic adjustment under DH stress.•Proline is not one of the defence strategies implemented for DH stress tolerance in edamame.