1. Ch. 3 Water Relations & Energy Dynamics

2. Water Potential Water in plants/soil has solutes: NEGATIVE
What tissue in plant carries water?

3. Water transport Xylem: water conducting tissue
What % water remains in plant?

4. Water transport Xylem: water conducting tissue Water in plant? <5%!
How water move? ?

5. Water transport Transpiration: evaporation from lvs.
Moves by pull (under tension)

6. Water transport
Ex:

7. Water potential tour.....
Soil to air pathway
Fig. 3.2a

8. Soil water g = +
total m p s
What determines psi soil?

9. Soil water What determines psi soil? Gravitational: unimportant= +
total m p s
What determines psi soil?
Gravitational: unimportant
Pressure: unimportant

10. Soil water solute potential: important _______ g = + total m p s
Dauphin Island: salt marsh

11. Soil water g = +
total m p s
matric potential: #1

12. Soil water Matric potential determined by texture
Soil pore space: air spaces
Clay most
Sand least

13. Soil water Water added, pores fill
1 ft soil ea. type
Water added, pores fill
Soil saturated: Saturation water content
Note sand<clay loam

14. Soil water
1.7
Gravity removes water:
Gravitational water
Most sand 3

15. Soil water 1.7 Allow gravity drain water: 3 Most sand
Gravitational water
Most sand
Now field capacity: fully charged 3

16. Soil water Plant use: becomes stressed
permanent wilting point (PWP): plant psi = ____
Mesophytes (“normal” plants), -1.5 MPa

17. Soil water 2 1 Field Capacity - PWP: available water capacity
Greatest loam, less clay, least sandy
1.8 2 1

18. Soil water
Unavailable water: hold too tight
Greatest clay, least sand

19. Soil water
Recap. Coarse: little water held, delivers little. Hold loose!
Fine: lots held, delivers good amt. but retains PWP. Hold tight!
Loam (& silt loam): hold
Fig.
4.9b

20. Soil water
Texture impacts infiltration: ability penetrate

21. Soil water Texture impacts infiltration: ability penetrate
Coarse soil: hi infiltration.
Structure important
Texture effect
Structure effect

22. Soil water Vertical movement : not always “a downer!”
Hydraulic lift: movement water by roots from deep to shallow
Soil dry:
Lo psi
water
Soil moist:
Hi psi

23. Soil water Ex, Acer saccharum (sugar maple) NY
Understory herbs: larger < 2 m from tree

24. Dew in soil Soil distillation: movement up Deserts hot cold med. Day
Nite
Water vapor
cold
warm
Relative temperatures in day and nite

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

26. Water in the plant: roots
Root: little cuticle (wax layer) on epidermis

27. Water in the plant: roots
Root must be near water. Why? Hydraulic conductivity: ability water move _____
Conductivity decreases as soil _____
How root contact more?
Wet
Dry

28. Water in the plant: roots
How root contact more?
1) Root hairs

29. Water in the plant: roots
How root contact more?
2) Grow!
Root biomass/productivity hi!
Shortgrass prairie root biomass = ______ total biomass!
CO prairie

30. Water in the plant: roots
How get to xylem?

31. Water in the plant: roots
2 ways:
apoplastic pathway: along walls (most water: 90%)
symplastic pathway: thru plasmodesmata (cell membrane connections)
Problem: Apoplastic pathway

32. Water in the plant: roots
Casparian strips (wax) in endodermis stop apoplastic pathway
Force

33. Water in the plant: stem xylem