Soil impact on plant hydraulics revealed by leaf rehydration kinetics
摘要
The hydraulic conductance of the soil is expected to become limiting for plant transpiration in drying soils. Specifically, coarse textured soils are expected to limit transpiration at less negative soil water potential (Ψsoil). Yet, there is still limited experimental evidence on Ψsoil and relative transpiration rate at which the decline in soil conductance impacts plant water status and the whole soil to plant hydraulic conductance. This gap is related to the lack of accurate and temporally resolved measurements of soil and plant water potential and hydraulic conductance.
MethodsWe combine rehydration techniques and water potential time-series measurements in wheat plants in two contrasting soil textures to measure the relative importance of soil and plant hydraulic conductance on stem water potential and transpiration rate.
ResultsWe found that during imposed water stress, a 50% reduction in transpiration rate was concomitant with the soil hydraulic conductance (Ksoil) falling below the plant hydraulic conductance (Kplant): Ksoil declined to 18–56% of Kplant in loam and to 7–39% in sand.
ConclusionsThe relative importance of soil and plant hydraulics was texture-specific, with coarse-textured soils imposing greater resistance on soil to leaf water flow at less negative Ψsoil than fine-textured soils. Upon rewetting, the soil–plant hydraulic conductance rapidly reached values it had before the plant was exposed to drying. These results highlight the soil-texture dependency of soil hydraulic properties on plant response to soil drying. The high temporal resolution and non-invasive experimental method is capable to resolve the effect of declining soil hydraulic conductance on the overall soil–plant conductance.
HighlightLeaf rehydration kinetics show that soil, not plant, limits water transport during drought—especially in coarse soils where hydraulic conductance drops at less negative water potential.