SOIL-ROOT INTERFACE WATER POTENTIAL IN Prunus×cistena GROWN IN DIFFERENT ARTIFICIAL MIXES

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The water potential at soil-root interface (Ψ_<s-r>), indicates soil water availability at the point of contact between the root and the soil. It is important in the pathway of water flow from the soil through the plant to the air. In this study, relations of Ψ_<s-r> with bulk soil water potential (Ψ_<soil>), xylem water potential (Ψ_<xylem>), and stomatal conductance (g_s) were established to estimate the value of Ψ_<s-r> and elucidate its response to soil texture. Three soil mixes made of composted bark, peat and sand (Mix-1), peat, bark, sand and compost (Mix-2), and peat, sawdust and sand (Mix-3), were used with Prunus×cistena, an ornamental shrub. After soil water was depleted to different levels, Ψ_<soil>, Ψ_<xylem>, g_s as well as transpiration rate (Tr) were measured. Ψ_<s-r> was calculated from these measured data. Plants grown in Mix-2 maintained higher Ψ_<s-r> until Ψ_<soil> decreased to -24 kPa, while Ψ_<s-r> in the plants grown in Mix-1 began to decrease at -5 kPa of Ψ_<soil>. Mix-3 showed a medium critical Ψ_<soil> for Ψ_<s-r> to decrease. Since there was a better soil water availability, plants in Mix-2 also showed a higher Ψ_<xylem> as well as higher gs and Tr as consequences. Plants in Mix-2 maintained better plant wacer status mainly by avoiding water stress. Plants in Mix-3 also avoided water stress, but it was, at least in part, attributed to less leaf area.
九州大学の論文