The effect of salinity on plant-available water
2017
Sheldon, Anna R. | Dalal, Ram C. | Kirchhof, Gunnar | Kopittke, Peter M. | Menzies, Neal W.
AIMS: Plant-available water is determined by soil matric and osmotic potential. The effect of salinity is a combination of the osmotic potential, the plant’s capacity to osmotically adjust, and the specific toxicity of the salt. Our aim was to better understand the relative importance of these components in a soil where the relationship between soil solution composition and soil water content had been characterized. METHOD: The capacity of wheat (Triticum aestivum L.) and chickpea (Cicer arietinum L.) to extract water from a saline soil was examined by imposing water stress on established plants, which were then grown until permanent wilting point (PWP) was reached. RESULTS: Wheat extracted soil moisture to lower potentials (−1.2 MPa) than chickpea (−0.80 MPa) in 0 NaCl treatments. Where salinity was low to moderate, plants extracted water to a PWP determined by the combined total of matric and osmotic potentials. Wheat extracted water to PWP in salinity treatments producing saturated-paste electrical conductivity (ECₛₑ) of up to 5.3 dS/m, and chickpea to 2.9 dS/m. CONCLUSIONS: As salinity increased, the effects of specific ion toxicity dominated, and water extraction by plants was significantly lower than that predicted on the basis of the total soil water potential.
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