1. Water movement in plants Biol 121, Fall 2010, Tom Buckley 04 Oct 10 Three functions: Replace transpired water (evaporation from leaves) Deliver nutrients from soil Supply water for new growth

2. Osmosis solute molecules (e.g., K + ) water molecules selectively permeable membrane X

3. cell

4. plasmolysis cell wall plasma membrane

5. cell

6. Wall stretching creates pressure

7. Water potential (  ): relative tendency of water to move by diffusion Osmotic potential (always ≤ 0) Turgor pressure ( ≥ 0 in living cells) ss pp  =  s +  p

8. Water potential (  ): relative tendency of water to move by diffusion Osmotic potential (always ≤ 0) Turgor pressure ( ≥ 0 in living cells) ss pp  =  s +  p Osmotic pressure  s

9. Water potential (  ): relative tendency of water to move by diffusion Osmotic potential ss  =  s +  p  s = -2.5 MPa  s = 0  p = 0  = -2.5 MPa  = 0 Water moves from higher  to lower   s = -RT∙[solutes] MPa  2.5 mol/L e.g.: [solutes] = 1 mol/L  s  -2.5 MPa

10.  =  s +  p  s = -2.5 MPa  s = 0  p = 0  = -2.5 MPa  = 0 plasmolysis

11. initial  s = -0.9 MPa  s = 0  p = 0  = 0  s = 0  p = +0.9 MPa  p = 0  = 0 turgor  = -0.9 MPa  s = -0.9 MPa

12. + + + + + + + + + Turgor pressure Active transport ATP ADP protons (H + ) proton pump ion channel + + + + + + + + + + cations (e.g., K + )

13. ATP Concentration gradients are a form of energy ADP

14. Growth= division+ expansion water uptake by osmosis

15. Q: Is the sequence shown at right an example of osmosis? (a)yes (b)no

16. Q: Which direction will water move? (a)from left to right (b)from right to left  s = -2  s = -1  p = +1  = -1  = 0 Cell #1 (LEFT) Cell #2 (RIGHT)

17. Water movement in plants Three functions: Replace transpired water (evaporation from leaves) Deliver nutrients from soil Supply water for new growth

18. Water movement in plants uptake by fine roots flow through xylem evaporation from leaves water potential: highest in soil lowest in leaves

19. Stoma Transpiration CO 2 H2OH2O

20. Fig 36.14 surface tension = negative pressure  =  s +  p stoma xylem negative in xylem Transpiration

21.  = -2 MPa = water in a drinking straw holding up 2 gallons

22. Delzon et al (2004) PCE 27:1077-1087 Pinus pinaster Transpiration  =  s +  p negative in xylem embolisms

23. vessel elements tracheids Fig 35.10 (in angiosperms) (in most vascular spp.)

24. bordered pits perforation plates Regulation of transpiration: xylem anatomy

25. Fig 36.14 closedopen ATP ADP protons (H + ) potassium (K + ) stoma xylem Regulation of transpiration: stomatal aperture pore

26. Fig 36.14 closedopen stoma xylem low light dry air dry soil high CO 2 high light humid air moist soil low CO 2 Regulation of transpiration: stomatal aperture

27. Phloem function companion cells sieve plate Fig 35.10 source (e.g., leaf) sink (e.g., bud or root)

28. Xylem vs Phloem xylemphloem conducts:watersugars conducting cells:deadalive pressure:negativepositive gymnosperms:tracheidsseive cells angiosperms:vessel elementsseive tube elements & tracheids

29. Root anatomy apical meristem root cap root hairs cortex vascular column (stele) Fig 35.13

30. uptake apoplastic symplastic Casparian Strip Fig 36.12 endodermis root hair