= Solute potential
{title2=$\Psi_s$}
= Osmotic potential
{synonym}
<Solute potential> is the contribution to <water potential> from dissolved material, with pure <water> assigned zero. In the nearly incompressible description, $\Psi_s=(RT/\bar V_w)\ln a_w$. In a dilute ideal <chemical solution>, $\Psi_s\simeq-RTc_{\mathrm{osm}}$, where $c_{\mathrm{osm}}$ is the <osmotic concentration> of dissolved particles. Thus <solute potential> is negative while the corresponding <osmotic pressure> is positive: $\Psi_s\simeq-\Pi$. This sign difference distinguishes a contribution to <water potential> from the compensating mechanical <pressure>.<Biology 2e by Mary Ann Clark and others/30.5 Transport of Water and Solutes in Plants>[Biology 2e, §30.5, Solute Potential: negative concentration contribution]{ref}
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