Variations in (A) photosynthetic assimilation (A), (B) transpiration rates (E), (C) stomatal conductance (g_s), and (D) predawn leaf xylem water potential (Ψ_L) in northern red oak seedlings as influenced by root volume category (RvC), ranging from the smallest (RvC1) to the largest (RvC4). Bars represent standard error of the mean. The dashed line separates period during which drought was imposed from resumption of irrigation.