TITLE:
Responses of Root Hydraulic Properties and Transpirational Factors to a Top Soil Drying in Cajanus cajan and Sesbania sesban
AUTHORS:
Nobuhito Sekiya, Hideki Araki
KEYWORDS:
Deep Roots; Drought; High Pressure Flow Meter; Hydraulic Resistance; Stomatal Aperture; Water Acquisition
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.4 No.12C,
December
20,
2013
ABSTRACT: Responses of leaf area (LA), stomatal conductance (gs), root length (RL) and root hydraulic conductance per unit of root length (Lpunit) 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 (ΨL) by reducing gs. 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 Lpunit. Sesbania kept constant levels of gs, causing a transient reduction of ΨL. ΨL of sesbania was, then, recovered by increasing only RL, but not Lpunit, 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 Lpunit and coordination among Lpunit, RL, gs and LA in exploitation of wet-deeper soils in response to top soil dryness.