1. Resource Acquisition and Transport in Vascular Plants

2. Green algae (ancestors of land plants) live in water.

3. Mosses (early plants) live in very moist environments, very low – non vascular

5. Land plants acquire resources:
CO2 O2
Light
Land plants acquire resources:
Above ground – carbon dioxide and sunlight
Below ground – water and minerals
H2O
Sugar
H2O
Minerals

6. Land plants compete for these resources.

7. CO2 O2
Natural selection favored the plants with efficient systems for long-distance transportation of
Water
Minerals
Products of photosynthesis
Light
H2O
Sugar
H2O
Minerals

8. Plants have to balance Acquisition of light and CO2
Evaporative loss of water

9. Various arrangement of leaves make it possible to maximize light and CO2 uptake and minimize water loss.
Leaves that are self shaded undergo programmed cell death and fall off because their photosynthetic output is less than their metabolic needs.

10. Roots undergo modifications to increase intake of water and minerals.
Roots associate with fungi to increase surface area (mycorrhizae)
Early association with land plants made colonization of land plants possible.

11. Transport occurs: Short distance: passive and active transport
Long distance: bulk flow

12. Cell membranes are fluid mosaic model made of
phospholipid bilayer
proteins

13. Most nutrients cannot diffuse across phospholipid bilayer
Active transport: cell must expend ATP (energy)
Transport proteins are involved in active transport of nutrients

14. Proton pump: energy from ATP pump protons, H+ out of the cells
inside of the membrane had –ve charge, outside has +ve charge: membrane potential
CYTOPLASM
EXTRACELLULAR FLUID
ATP
Proton pump
generates mem-
brane potential
and gradient.

15. Proton pump facilitates cation uptake
CYTOPLASM
EXTRACELLULAR FLUID
Cations ( , for
example) are
driven into the cell
by the membrane
potential.
Transport protein
Membrane potential and cation uptake

16. Proton pump facilitates cotransport of anions with H+
Cell accumulates
anions ( ,
for example) by
coupling their
transport to; the
inward diffusion
of through a
cotransporter.
Cotransport of anions

17. Proton pump facilitates transport of neutral solutes with H+
Plant cells can
also accumulate
a neutral solute,
such as sucrose
( ), by
cotransporting
down the
steep proton
gradient.
Cotransport of a neutral solute

18. Osmosis (diffusion of water) across semipermeable membrane.
Concentration of water determines direction of water flow
Water flow is affected by rigid cell walls which exerts pressure on plasma membrane.

19. Water potential (y): The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure; units megapascals (MPa).
Water potential refers to water’s potential energy – water’s capacity to perform work when it moves region of high water potential to a region of low water potential.

20. y = ys + yp Where: y = water potential
ys = solute potential/ osmotic potential
yp = pressure potential

21. Free water has highest water potential
Free water has highest water potential. When bound to solutes water potential goes down.

22. Pressure potential can be positive or negative.
Usually cells are under positive water potential. Usually cell contents press against cell wall and cell wall presses against protoplast – turgor pressure.

23. Water potential and water movement in an artificial model.
a) In absence of pressure ys determines net movement’
Addition of
solutes
0.1 M
solution
Pure
water
H2O
P = 0
S = –0.23
 = 0 MPa
P = –0.23 MPa

24. b) Positive pressure can raise y by increasing yp.
Applying
physical
pressure
b) Positive pressure can raise y by increasing yp.
H2O
P = 0
S = –0.23
 = 0 MPa
P = –0 MPa

25. c) Raising y on the right causes movement to the left.
Applying
physical
pressure
c) Raising y on the right causes movement to the left.
H2O
P =
S = –0.23
 = 0 MPa
P = –0.07 MPa

26. Negative
pressure
d) –ve pressure reduces yp, causes net movement to the left by reducing y .
H2O
P = –0.30
P =
S = –0.23
S = –0.23
P = –0.30 MPa
P = –0.23 MPa

27. It becomes turgid when placed in pure water.
Initial flaccid cell undergoes plasmolysis when placed in an environment with high solute concentration.
It becomes turgid when placed in pure water.
Initial flaccid cell: 
P = 0 
S = –0.7
0.4 M sucrose solution: 
P = –0.7 MPa
Distilled water: 
P = 0 
P = 0 
S = –0.9 
S = 0 
P = –0.9 MPa 
P = 0 MPa

28. What happens when you forget to water a plant
What happens when you forget to water a plant? What happens when you water it?

29. Water transport is aided by transport proteins – aquaporins.

30. Three major pathways of transport:
Apoplastic route
Symplastic route
Transmembrane route
Key
Symplast
Apoplast
Transmembrane route
Apoplast
Symplast
Symplastic route
Apoplastic route
Transport routes between cells

31. Bulk flow requires more efficient transport than diffusion and active transport.

32. Transport of water and minerals into the xylem: pushing and pulling

33. Pushing up the xylem sap: root pressure
Casparian strip
Endodermal cell
Pathway along
apoplast
Pathway
through
symplast
Pushing up the xylem sap: root pressure
Casparian strip
Plasma
membrane
Apoplastic
route
Vessels
(xylem)
Symplastic
route
Root
hair
Epidermis
Endodermis
Vascular cylinder
Cortex

34. When too much enters plants give out excess water through leaves – guttation

35. Transpiration: loss of water vapor through leaves and other aerial parts of plants. A single corn plant transpires 60L of water in the growing season.

36. Transpiration pull Y = –0.15 MPa Y = –10.00 MPa Cell wall Air-water
LE 36-12
Transpiration pull
Y = –0.15 MPa
Y = –10.00 MPa
Cell wall
Air-water
interface
Airspace
Low rate of
transpiration
High rate of
transpiration
Cuticle
Upper
epidermis
Cytoplasm
Evaporation
Mesophyll
Airspace
Air
space
Cell wall
Lower
epidermis
Evaporation
Water film
Vacuole
Cuticle
Stoma
CO2 O2
CO2 O2
Xylem

37. Leaf (cell walls) = –1.0 MPa
Cohesion and adhesion causes ascent of sap
Xylem
sap
Outside air 
= –100.0 MPa 
Mesophyll
cells
Stoma
Leaf (air spaces)
= –7.0 MPa 
Water
molecule
Transpiration
Leaf (cell walls) = –1.0 MPa 
Atmosphere
Xylem
cells
Adhesion
Cell
wall
Water potential gradient
Trunk xylem
= –0.8 Mpa 
Cohesion, by
hydrogen
bonding
Cohesion and
adhesion in
the xylem
Water
molecule
Root
hair
Root xylem
= –0.6 MPa 
Soil
particle
Soil
= –0.3 MPa 
Water
Water uptake
from soil

38. Stomata regulates rate of transpiration: opening and closing of stomata are regulated by transport of K+.
Cells turgid/Stoma open
Cells flaccid/Stoma closed
H2O
H2O
H2O
H2O K+
H2O
H2O
H2O
H2O
H2O
H2O
Role of potassium in stomatal opening and closing

39. Cells turgid/Stoma open
Cells flaccid/Stoma closed

40. Adpatations in desert plants
Reduced life cycle
Reduced period of leaf production
Thicker cuticle
Bristles to reflect the heat
Reduced leaves, photosynthetic stems
Growing underground
Taking carbon dioxide at night

41. Cuticle
Upper epidermal tissue
Lower epidermal
tissue
Trichomes
(“hairs”)
Stomata
100 µm

42. Reduced leaves, photosynthetic stems

43. Movement of sugars from source to sink
Translocation: transport of photosynthetic products for use and storage by phloem tissue.
Sugar source: plant organ that is the net producer of sugar (leaves)
Sugar sink: net consumer of depository sugar (growing tips, roots, buds, stems, fruits)

44. Positive pressure bulk flow in sieve tubes (phloem).
Vessel
(xylem)
Sieve tube
(phloem)
Source cell
(leaf)
H2O
Sucrose
H2O
stream
flow
Pressure
Transpiration
Sink cell
(storage
root)
Sucrose
H2O

45. Thinning helps prevent excess demand on sugar source (pruning in agriculture)