LabBench Activity

Guard Cell Function

Stomatal closing

  1. Potassium ions move out of the vacuole and out of the cells.
  2. Water moves out of the vacuoles, following potassium ions.
  3. The guard cells shrink in size.
  4. The stoma closes.

Stomatal opening

  1. Potassium ions move into the vacuoles.
  2. Water moves into the vacuoles, following potassium ions.
  3. The guard cells expand.
  4. The stoma opens.