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NOTES: CH 36 - Transport in Plants

NOTES: CH 36 - Transport in Plants. Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

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Page 1: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

NOTES: CH 36 - Transport in

Plants

Page 2: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Recall that transport across the cell membrane of plant cells occurs by:

-diffusion

-facilitated diffusion

-osmosis (diffusion of water)

-active transport (done by transport proteins)

Page 3: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 4: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

PROTON PUMPS:

● pump out H+ ions, producing a proton gradient (more H+ outside cell) and a membrane potential (inside is negative relative to outside)

Page 5: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

• this “stored” energy is used to transport other molecules across the membrane:-K+ ions pulled into cell-sugar molecules are loaded into companion cells via COTRANSPORT

**These are all examples of CHEMIOSMOSIS

Page 6: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 7: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 8: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

WATER POTENTIAL (): predicts the direction water will flow

● combines solute concentration (osmotic potential, s) with differences in pressure

(pressure potential, p)

Page 9: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

WATER POTENTIAL ()● as solute conc. increases, s decreases

● as pressure (hydrostatic) increases, p

increases

= s + p

● water flows from HIGH water potential to LOW water potential!

Page 10: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 11: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

● PLASMOLYSIS: when a plant cell loses water by osmosis; protoplast pulls away from cell wall

 

● TURGOR PRESSURE: develops when a plant cell gains water by osmosis

Page 12: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Recall the 3 major parts of a plant cell:1) cell wall2) cytosol / cytoplasm3) vacuole (surrounded by TONOPLAST)

Page 13: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

● SYMPLAST: continuum of cytoplasmic compartments of neighboring cells; connected by PLASMODESMATA

● APOPLAST: continuum of adjacent cell walls and intercellular spaces

Page 14: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 15: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Lateral / short-distance transport can occur:

1) across cell membranes (trans-membrane route)

2) via the SYMPLASTIC ROUTE (molecules travel through the plasmodesmata)

3) via the APOPLASTIC ROUTE (molecules don’t enter cells)

Page 16: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 17: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Vertical / long-distance transport occurs by:

1) BULK FLOW: movement due to pressure differences (substances move from regions of higher to lower pressure)

2) TRANSPIRATION: creates tension which “pulls” sap up through the xylem from the roots

3) HYDROSTATIC PRESSURE: builds up at one end of phloem vessels; forces sap to the other end of the tube

Page 18: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 19: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Absorption of Water & Minerals by Roots:

● Transport pathway:

*soil epidermis root cortex xylem

 

-minerals moving through symplastic route move directly into vascular tissues

Page 20: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 21: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

-minerals & water moving through apoplastic route are blocked at the endodermis by the CASPARIAN STRIP (a ring of waxy substance, SUBERIN) and must enter an endodermal cell

 

**this ensures that all minerals entering the STELE pass through at least one selectively permeable membrane.

Page 22: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Transport of Xylem Sap● xylem sap flows upward at 15 m per hour

● is it pushed from below or pulled from above?

● root pressure builds up when transpiration is slow (i.e. at night); this causes GUTTATION

● this only accounts for small amt. of xylem transport

Page 23: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 24: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Transport of Xylem Sap

● most xylem sap moves via the mechanism of: TRANSPIRATION-COHESION-TENSION

Page 25: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

TRANSPIRATION-COHESION-TENSION:

● TRANSPIRATION: (loss of water from leaf cells through stomata) creates negative pressure

Page 26: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

TRANSPIRATION-COHESION-TENSION:

● neg. pressure pulls water from the xylem

● transpiration pull on xylem sap is transmitted from one water molecule to another through COHESION (due to H-bonds between water molecules)

Page 27: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 28: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 29: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 30: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

THE CONTROL OF TRANSPIRATION stomata provide openings in leaf tissue

for the transpiration of water (out of leaf) and the diffusion of CO2 into the leaf for

photosynthesis

GUARD CELLS surrounding the stomata regulate the requirements for photosynthesis with the

need to conserve water

Page 31: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 32: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Adaptations to reduce water loss:

more stomata on bottom of leaves

waxy leaf cuticle on rest of leaf surface

Page 33: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Benefits of transpiration:

assists in mineral transfer from roots shoots

evaporative cooling

Page 34: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Stomatal Opening / Closing: GUARD CELLS: cells that flank the

stomata and control stomatal diameter by changing shape:

-when TURGID, guard cells

“buckle” and stomata

open

-when FLACCID, guard

cells sag and

stomata close

Page 35: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 36: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

a change in turgor pressure in guard cells results from the reversible uptake of K+

*when K+ leaves cell,

s increases

H2O is lost stomata close

*when K+ enters cell,

s decreases H2O is taken up stomata open

Page 37: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

  Studies show that K+ fluxes across guard cell membrane are likely coupled to membrane potentials created by PROTON PUMPS

Page 38: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 39: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Stomata open at dawn in response to:

1) Light: induces K+ uptake; activates a blue-light receptor which drives photosynthesis ATP

2) Decrease of CO2 in air spaces due to

photosynthesis

3) internal clock in guard cells (CIRCADIAN RHYTHM = 24 hour cycle)

Page 40: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Guard cells may close during daytime if:

1) there is a water deficiency

flaccid guard cells

2) production of abscisic acid (hormone); in response to water deficiency; signals guard cells to close

3) high temperature increases CO2 in air

spaces due to increased respiration

Page 41: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 42: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 43: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Xerophytes have special adaptations:

small, thick leaves

thick cuticle

stomata are in depressions on underside of leaves

some shed leaves

during driest time of year

cacti store water in stems during wet season

Page 44: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Translocation of Phloem Sap

TRANSLOCATION = transport of products of photosynthesis by phloem to rest of plant

PHLOEM SAP = sucrose, minerals, amino acids, hormones

Page 45: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

phloem sap moves through sieve tubes from a SUGAR SOURCE (production area) to a SUGAR SINK (use or storage area)

Sugars move into sieve tubes via symplastic and/or apoplastic routes 

Sucrose is “loaded” into cells at the source end by active transport (COTRANSPORT)

Sucrose is “unloaded” at the sink end of sieve tubes

Page 46: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis
Page 47: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis

Pressure Flow / Bulk Flow of Phloem Sap

pressure builds up at source end (phloem loading s decreases water enters tubes hydrostatic pressure)

pressure is released at sink end (phloem is unloaded s outside tube decreases water leaves release of hydrostatic pressure)

Page 48: NOTES: CH 36 - Transport in Plants.  Recall that transport across the cell membrane of plant cells occurs by: -diffusion -facilitated diffusion -osmosis