Absorption and Transport Chapter 11. Fig. 11-1, p. 164 H2OH2O product of photosynthesis (sucrose) H...
Transcript of Absorption and Transport Chapter 11. Fig. 11-1, p. 164 H2OH2O product of photosynthesis (sucrose) H...
Absorption and Transport
Chapter 11
Fig. 11-1, p. 164
H2O
product ofphotosynthesis
(sucrose)
H2O vapor
H2O vapor
H2O vapor
H2O
mineral ions
Fig. 2-6, p. 18
slight negative charge at this end
slight positive charge at this end
but the wholemolecule hasno net charge(+ and – balanceeach other)
Hydrogen bonds in water
Fig. 11-2a, p. 165
water vapor molecules
(1) Diffusion
Fig. 11-2b, p. 165
Differentially permeablemembrane (water goes through, but not starch)
starch solution
waternet flow
(2) Osmosis
Fig. 11-2b, p. 165
(3) Hydrostatic pressure
• Involves osmosis and the cell wall.
Fig. 2-10, p. 22
Polysaccharides:• Cellulose (cellular structure)
- monomer is glucose
- connected in a straight chain
- cellulose molecules bind with each other via hydrogen bonds, resulting in cellulose microfibers
• Starch (energy storage)
- monomer is glucose
- connected in a helix
Fig. 3-7 (a-c), p. 36
PROTOPLAST SOLUTION
Concentration0.3 molar(Isotonic)
Concentration0 molar(Hypotonic)
Concentration0.27 molar
Pressure0.66 megapascals
Concentration0.5 molar(Hypertonic)
Concentration0.3 molar
Pressure0 megapascals
Concentration0.5 molar
Pressure0 megapascals
(3) Hydrostatic pressure in
cells
Turgor pressure is one type of hydrostatic pressure. Turgor pressure is the result of a combination of osmosis and cell wall rigidity.
Fig. 3-7 (d), p. 36
Plasmolyzed cells
Fig. 11-2c, p. 165
force pullingwater along side of tubeair-water interface
capillary tube
water tension inwater column
water moleculesconnected byhydrogen bonds
force pullingthe air-waterinterfacestraight
(4) Capillary forces
(5) Gravity
• Gravity– Takes force to move water upward– Significant factor in tall trees
Transpiration
Fig. 11-5, p. 168
cuticle is relativelyimpermeableto H2O
water-filledxylem in vein
cell wall permeatedwith H2O
air not saturated
water-filledleaf cells
substomatal cavity (intercellular space)
Fig. 11-3, p. 167
thin boundarylayer; steepgradient; fastdiffusion
thick boundarylayer; gentlegradient; slowdiffusion
Boundary layer: an unstirred layer of air close to the leaf
Bulk air: air outside of the boundary layer
Wind stirs up the air close to the leaf and makes the boundary layer thinner. Plants transpire much faster on a windy day than on a still one.
Fig. 11-4, p. 167
sunken stomata
spongyparenchyma
fibers sunken stomata
cuticle stomatalcrypts
Cross section of a yucca leaf
Flow of Water Into Leaves
Fig. 11-6, p. 168
Capillary forces can convert Water loss into a tension within a tracheid.Before evaporation, there is little tension. After evaporation, there is high tension.
Dots: water moleculesShort lines: forces of cohesion and adhesion
Pits
A. B.
Tension in the water pulling the tracheid wall inward.
Capillary forces pulling water into the tracheid
Fig. 4-11, p. 58
pitsin wall
one vesselmember
perforationplate
Tracheary elements comparedVessel members Tracheids
Vessel members join end to end, but they digest out the end walls forming a tube called a vessel.
Tracheids join end to end and along their sides and are connected by bordered pits.
Fig. 11-1, p. 164
H2O
product ofphotosynthesis
(sucrose)
H2O vapor
H2O vapor
H2O vapor
H2O
mineral ions
Fig. 11-7, p. 169
plasmodesma
symplastic flow
apoplastic flow
cell wall
cytoplasm
xylem
epidermis cortex stele
Casparian stripof endodermis
symplastof endodermis
roothair
Symplastic and apoplastic flow through roots
Control of Water Flow
• Environmental factors affecting rate of transpiration– Temperature– Relative humidity of bulk air– Wind speed
Control of Water Flow
• Transpiration– Slow at night– Increases after sun comes up– Peaks middle of day– Decreases to night level over afternoon
• Rate of transpiration directly related to intensity of light on leaves
Fig. 11-8a, p. 170
plasmamembrane
protonpump
starch
malic acid
malate–
ATP
ADP+ Pi
K+
K+
H+
H+
CI
CI
Events leading to the opening of a stoma:
The production of malate and the influx of K+ and Cl- powered by the electrical and pH gradients produced by the proton pump increase the concentration of osmotically active solutes in the guard cells. As a result, water flows into the cells by osmosis.
LIGHT
H+
Fig. 11-9a, p. 170
cells connected
With increased pressure, cell getslonger. Because the outer wall canexpand more readily, cell bowsoutward.
reinforced inner wall
cellulose microfibrils(radial micellation)
How radial micellation and reinforcement of guard cell walls force an expanding cell to bow outward.
Fig. 11-9b, p. 170