the chapter 29 homework is due on monday, march 30 at 11:59 pm the chapter 29 test is on tuesday,...

• The Chapter 29 Homework is due on Monday, March 30 at 11:59 pm

• The Chapter 29 Test is on Tuesday, March 31.

Chapter 29Transport and Water Potential

You Must Know• How passive transport, active transport, and

cotransport function to move materials across plant cell membranes.

• The role of water potential in predicting movement of water in plants.

Concept 29.1: Adaptations for acquiring resources were key steps in the evolution of vascular plants

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Figure 29.2-1

H2Oandminerals

H2O

Xylem

The plant does not have to expend any energy to transport water through the xylem

What substances do plants need for photosynthesis?

What substances do plants need for respiration?

Figure 29.2-2

H2Oandminerals

H2O

O2

CO2

O2CO2

Figure 29.2-3

Light

H2Oandminerals

H2O Sugar

O2

CO2

O2CO2

Phloem transports photosynthetic products from sources to sinks.

• Video clip of water transport.

• Adaptations in each species represent compromises between enhancing photosynthesis and minimizing water loss.

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Sugarcane Corn Switch grass

CYTOPLASM EXTRACELLULARFLUID

Protonpump

Hydrogen ion

(a) H+ and membrane potential

H+

H+

H+

H+

H+

H+

H+

H+

Figure 29.5 Solute transport across plant cell plasma membranes

Sucrose(neutral solute)

(b) H+ and cotransport of neutral solutes

H+/sucrosecotransporter

S H+ H+

H+H+

H+

H+

H+

H+

H+

H+

H+

S

S

S

S

S

Nitrate

(c) H+ and cotransport of ions

H+/NO3−

cotransporter

NO3−

H+

H+

H+

H+

H+

H+H+

H+

H+H+

H+

NO3

−

NO3−

NO3−

NO3−

NO 3−

Potassium ion

Ion channel

(d) Ion channels

K+

K+

K+

K+

K+ K+

K+

Short-Distance Transport of Water Across Plasma Membranes

• To survive, plants must balance water uptake and loss.

• Osmosis determines the net uptake or water loss by a cell and is affected by solute concentration and pressure.

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• Water potential is a measurement that combines the effects of solute concentration and pressure.

• Water potential determines the direction of movement of water.

• Water flows from regions of higher water potential to regions of lower water potential.

• Potential refers to water’s capacity to perform work.

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• Water potential is abbreviated as and measured in a unit of pressure called the megapascal (MPa)

• 0 MPa for pure water at sea level and at room temperature.

S P

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• Turgor pressure is the pressure exerted by the plasma membrane against the cell wall, and the cell wall against the protoplast.

© 2014 Pearson Education, Inc.

FlaccidTurgid

−0.7

Figure 29.6b

Initial flaccid cell:

−0.7 MPa

P

S

Turgid cellat osmoticequilibriumwith itssurroundings

Pure water:

(b) Initial conditions:cellular environmental

0 MPa

00

P

S

0 MPa

0.7

P

S

0

−0.7

−0.9

Figure 29.6a

Plasmolyzedcell at osmoticequilibriumwith itssurroundings

0.4 M sucrosesolution:

(a) Initial conditions:cellular environmental

−0.9 MPa

−0.9

P

S

Initial flaccid cell:

−0.9 MPa

P

S

−0.7 MPa

−0.7

P

S

0

0

0