Stomata control

• how does high light intensity influence the opening of stoma?

  • Potassium ions increase concentration of the solution in guard cells (accumulate within them)
  • Water moves into guard cells by osmosis because the water potential decreases
  • Cell swells unevenly as turgor increases (so stoma opens)
  • because inner (thicker) wall is less flexible than outer (thinner) wall
• What does ABA control?

  Closing of stomata in abiotic (water) stress
• How does ABA influence stomata closing during abiotic stress

  • ABA released- stomata closure
  • Roots provide early warning system
  • Soil WP lowers
  • Roots produce ABA
  • ABA transported to leaves
  • ABA binds to receptors on guard cells
  • ABA causes changes in ion concentration in guard cells (potassium ions pumped out)
  • WP decreases in adjacent cells and guard cells lose water
  • Stomata closes and less water lost by transpiration
• How does ABA initiate stomata closing?

  • Either produced by cells in the leaf or produced in the roots when they detect low WP levels in the soil, after which ABA is transported to leaf
  • ABA binds to receptors on plasma membrane of guard cells
  • ABA activates changes in ionic conc of guard cells, so WP is reduced in the guard cells, therefore turgor is reduced
  • Guard cells become flaccid, stomata close and transpiration is reduced
• Why is it important to regulate stomatal control?

  • stomata need to open to cool the plant when the plant is too warm as water evaporates from the cells in the leaves
  • stomata need to close to conserve water and prevent water loss through transpiration
• what hormone controls the opening and closure of stomata?

  ABA