Responses of leaf area (LA), stomatal conductance (g_s), root length (RL) and root hydraulic conductance per unit of root length (Lp_unit) to top soil dryness were investigated. Pigeon pea (Cajanus cajan) and sesbania (Sesbania sesban) were grown in a vertical split-root system. From sixty-six days after sowing, the top soil was dried while the bottom soil was kept wet. Pigeon pea increased LA while maintaining leaf water potential (Ψ_L) by reducing g_s. Increased transpirational demand through canopy development was compensated for by increasing water extraction in the bottom soil. This was achieved by increasing not only RL but also Lp_unit. Sesbania kept constant levels of g_s, causing a transient reduction of Ψ_L. Ψ_L of sesbania was, then, recovered by increasing only RL, but not Lp_unit, in the bottom soil while suspending LA extension, suggesting that sesbania regulated only the root area to LA ratio. This study demonstrated a species-specific significance of Lp_unit and coordination among Lp_unit, RL, g_s and LA in exploitation of wet-deeper soils in response to top soil dryness.