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Article Addendum
A Model Based on Facilitated Passive Diffusion is Needed to Describe Root Water Entry through Aquaporins
P.C. Beaudette, C. Salon and R.J.N. Emery
volume 2 | issue 5
september/octoberPages: 401 - 403
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Despite abundant evidence that water transfer from soil to xylem occurs along a pathway regulated by aquaporins (AQPs) water entry is still modeled using principles of ordinary passive diffusion. Problems with this model have been known for some time and include variable intrinsic properties of conductivity Lp, changing reflection coefficients,σ and its inability to accurately resolve osmotic differentials between the soil and xylem. Here we propose a model of water entry based on principles of facilitated passive diffusion and following Michaelis-Menten formalism. If one accepts that water entry is controlled, at least in part, by AQPs, then a model of ordinary passive diffusion is precluded, as it does not allow for facilitation kinetics. By contrast, recognition of facilitated water entry through protein channels could explain shortcomings of ordinary passive diffusion, such as diurnal variability in conductivity which we have recently shown is directly correlated to diurnal changes in PsPIP2-1 mRNA levels in Pisum sativum.
Authors
P.C. Beaudette
Trent University, Peterborough, Ontario, Canada
C. Salon
Trent University, Peterborough, Ontario, Canada
R.J.N. Emery
Trent University, Peterborough, Ontario, Canada
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDF If the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.