Equilibrium potential (K+, guard cell)

 

Plants exchange gases through pores called stomates found on leaves. The pores are bordered by two guard cells that change shape to open and close the stomate as seen in the figure.  The following are labeled on the closed stomate:

●      potassium (K+) ion concentrations (measured in mM) inside and outside the guard cell

●      membrane potential (-30 mV)

●      K+ channel

 

a) When stomates are closed, there is net movement of K+ ions out of the guard cell through the K+ channel (as indicated by the arrow). To open a stomate, water must enter guard cells to change their shape.  To accomplish this, K+ ions move INTO the guard cell instead of out.

What could change to cause net movement of K+ INTO the closed guard cell? Identify as many ways as you can.

 

b) Explain how the ways you identified above cause K+ to move INTO the closed guard cell.

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This material is based upon work supported by the National Science Foundation (DUE grants: 1438739, 1323162, 1347740, 0736952 and 1022653). Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.