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 grown under well watered conditions (WW), low moisture stress (LMS), medium moisture stress (MMS), and high moisture stress (HMS) as induced by drought under greenhouse environments. Bars represent standard error of the mean. The dashed line separates period during which drought was imposed from resumption of irrigation.