1. Ch. 3 Water Relations/Energy Balance

2. Water potential tour..... Examine soil to air pathway of water Fig. 3.2a

3. Water in the plant: stem xylem

4. Xylem cells –Vessels vs. tracheids

5. Water in the plant: stem xylem Water cohesion (stick together) Water adhesion (stick charged surfaces: cell walls)

6. Water in the plant: stem xylem Adhesion: –Slows movement –Strengthens ________ Small dia. cells: more water-wall contact/unit vol. (withstand ________)

7. Water in the plant: stem xylem SO: plants (or parts) under stress make small cells! Ex, Sequoiadendron gigantea (big tree)

8. Water in the plant: stem xylem 102 ft. around 2,145 tons Boyd Bro: 1984!

9. Water in the plant: stem xylem Conifer: tracheids Smaller @ top (psi lowest)

10. Water in the plant: stem xylem Other small cells: –desert plants (Larrea: creosote bush)

11. Water in the plant: stem xylem Other exs. small cells: –salt marsh plants Salicornia virginica

12. Water in the plant: leaf Steepest drop psi b/w leaf/air

13. Water in the plant: leaf Air “dry:” Most plants wilt when soil psi = -1.5 Mpa (permanent wilting point: can’t recover) –Humidity > 97% to be -1.5 MPa or greater -1.5 MPa

14. Water in the plant: leaf Water exits thru: –epidermis (cuticular transpiration): <10% –stomates (stomatal transpiration): most loss Fig. 3.9a Fig. 3.9b

15. How control leaf water loss? 1) Cuticle Ex: Cakile constricta

16. How control leaf water loss? 2) Stomate properties –Density: few saves water –But

17. How control leaf water loss? 2) Stomate properties –Density affected: light, temp., CO 2 (more CO 2 -- density less) –Density change last 200 yr?

18. How control leaf water loss? 2) Stomate properties –Arrangement: top/bottom –Often: more

19. How control leaf water loss? 2) Stomate properties –Behavior: close stomates--abscisic acid Abscisic acid

20. How control leaf water loss? 3) Boundary layer Boundary layer (BL): Slow-flowing Water diffuses (slow) Thick BL slows loss

21. How control leaf water loss? 3) BL thickness BL thickness (delta) –Decreases as wind increases –Increases as leaf size –Big leaves—thick

22. How control leaf water loss? 3) BL thickness How increase BL thickness? –Increase leaf Magnolia macrophylla Ceratiola ericoides

23. How control leaf water loss? 3) BL thickness How increase BL thickness? –entire

24. How control leaf water loss? 3) BL thickness How increase BL thickness? –Do NOT divide blade

25. How control leaf water loss? How increase BL w/o change leaf dimensions? Hairs (trichomes) or spines (modified ______)

26. How control leaf water loss? Stomatal crypts: stomates

27. How control leaf water loss? Increases dist. H2O diffuses (slows loss) BL

28. How control leaf water loss: Review

29. Dew (Good and Bad) Dew: Water condensation Good dew: Reduce loss –increases

30. Bad Dew CO 2 diffuses 10,000x slower H2O than air –Decrease CO 2 uptake Response: unwettable leaves Leaf from cloud forest plant