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• The Chapter 29 Homework is due on Monday, March 30 at 11:59 pm
• The Chapter 29 Test is on Tuesday, March 31.
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
© 2014 Pearson Education, Inc.
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.
© 2014 Pearson Education, Inc.
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.
© 2014 Pearson Education, Inc.
• 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.
© 2014 Pearson Education, Inc.
• 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
© 2014 Pearson Education, Inc.
• 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
