Seedling regeneration techniques affect root systems and the response of Quercus robur seedlings to water shortages

•Q. robur response to water shortage depends on plant regeneration origin.•Root morphology is more sensitive to water shortage than biomass allocation.•Carbohydrates from taproots are predominantly mobilized under water shortage.•Coppiced and root-pruned oaks relied on stored carbohydrates to respond to water shortage.