1. Chapter 36 Notes
Transport in Plants

2. Concept 36.1

3. Concept 36.1 Transport in plants occurs on 3 levels
- the uptake and loss of water by individual cells
- short distance transport of substances from cell to cell at the level of tissues and organs
- long distance transport of sap within xylem and phloem of the whole plant

4. Concept 36.1 Uptake and loss of water by cells
- plant cell membranes are selectively permeable
- use of transport proteins /selective channels
- transport can be active or passive

5. Concept 36.1
- proton pump: hydrolyzes ATP and uses the released energy to pump H+ ions out of the cell
- forms a H+ gradient
- plant cells use the energy from the gradient to drive the transport of many different solutes
- ex. movement of K+

6. Concept 36.1

7. Concept 36.1
Differences in water potential drive water transport in plant cells
Osmosis: the net uptake or loss of water by a cell
- high concentration to low
In plants, the cell wall makes physical pressure a factor of osmosis

8. Concept 36.1
Water potential: the combined effect of solute concentration and pressure.
- psi (Y)
- water will move from the solution with the higher water potential to the solution with the lower water potential

9. Concept 36.1

10. Concept 36.1 The combined effects of pressure and concentration
- Y = YP + YS
- YP: pressure potential
- YS: solute potential

12. Concept 36.1

13. Concept 36.1 Bulk flow functions in long distance transport
Bulk flow: the movement of fluid driven by pressure
- water and solutes move the xylem vessels and sieve tubes
- transpiration reduces pressure in xylem which creates tension

14. Concept 36.2 Most absorption occurs near root tips
- soil particles adhere to root hairs
- the soil sln. flows into the walls of the epidermal cells and into the root cortex
- mycorrhizae absorb water and minerals and then transfers them to the plant

15. Concept 36.2

16. Concept 36.2

17. Concept 36.3
Root pressure: water flows in from the root cortex, generating a positive pressure that forces fluid up the xylem
Root pressure causes guttation: when more water enters leaves than is transpired and the excess is forced out
Root pressure can only force water up a few meters, not the major force

18. Concept 36.3
Pulling up xylem sap: Transpiration-Cohesion-Tension Theory
Transpiration
-when stomata open water exits the leaf
- move from [high] to [low]

19. Concept 36.3

20. Concept 36.3
Cohesion
- water molecules will bond to each other with hydrogen bonds
- water molecules exiting the xylem tug on adjacent molecules
- the pull is relayed

21. Concept 36.3
Tension
- the upward pull creates tension within the xylem
- the small diameter of the tracheids helps overcome the force of gravity