A split-rooted containerized system was developed by approach grafting two, 1-year-old apple (Malusxdomestica Borkh. cv 'Gala') trees to investigate the effect of soil moisture heterogeneity and total soil moisture content (θv) on tree water relations, gas exchange, and leaf abscisic acid (ABA) concentration [ABA[subscript leaf]]. Four irrigation treatments comprising a...