≤1 ion/200,000 water molecules
||African clawed frog Xenopus laevis
||Maurel C. Aquaporins and water permeability of plant membranes. Annu Rev Plant Physiol Plant Mol Biol. 1997 Jun48: 399-429. p.414 2nd paragraphPubMed ID15012269
||Maurel C, Reizer J, Schroeder JI, Chrispeels MJ. 1993. The vacuolar membrane protein g-TIP creates water specific channels in Xenopus oocytes. EMBO J. 12: 2241–47PubMed ID8508761
||"In particular, current measurements during osmosis
did not indicate any detectable passive ion permeability or any solvent-drag of
ions in conditions where the water channels were known to operate, indicating
the eventual passage of at most 1 ion for every 2X10^5 water molecules (primary source)."