Demystifying Osmotic Potential: One Factor in the Plant Water Potential Equation

 

Tested Studies in Laboratory Teaching, 2015, Volume 36

Rosemary H. Ford

Abstract

Water potential in plants depends on osmotic and pressure potentials. Pressure potential is easily understand by monitoring changes in tissue mass when immersed in various sugar solutions. Osmotic potential can be visualized by comparing the cell sap's density with these same sugar solutions in which it will rise, sink, or hover, where the latter represents the concentration of equal density, which suggests an isosmotic condition. Students can use this method to compare the density of various plant tissues (e.g. potato vs apple) or construct a Hoefler plot using the Van't Hoff equation to illustrate relationships between osmotic and pressure potential.

Keywords:  plant physiology, osmotic potential, water potential

University of Oregon (2014)