chapter 29 transpiration and unusual plants. you must know how the transpiration cohesion-tension...
TRANSCRIPT
You Must Know
• How the transpiration cohesion-tension mechanism explains water movement in plants.
Indian pipe, a nonphoto-synthetic parasite ofmycorrhizae
Epiphytes, Parasitic Plants, and Carnivorous Plants
• Some plants have nutritional adaptations that use other organisms in nonmutualistic ways.
• Three unusual adaptations are– Epiphytes– Parasitic plants– Carnivorous plants
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Pitcher plants
Concept 29.5: Transpiration drives the transport of water and minerals from roots to shoots via the xylem
• Plants can move a large volume of water from their roots to shoots.
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Absorption of Water and Minerals by Root Cells
• The concentration of essential minerals is greater in the roots than in the soil because of active transport.
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Apoplastic route
Cell wall
Symplastic route
Transmembrane route
Cytosol
KeyPlasmodesma
Plasma membrane Apoplast
Symplast
Cell compartments and routes for short-distance transport
Figure 29.16a
Apoplasticroute
Symplasticroute
Transmembraneroute
Apoplasticroute
Symplasticroute
Roothair
Plasmamembrane
Epidermis
Casparian strip
Vascularcylinder(stele)
Vessels(xylem)
Cortex
Endodermis
Transport in the xylem
1
12
2
3
3
5
5
Bulk Flow Transport via the Xylem
• Xylem sap, water and dissolved minerals, is transported from roots to leaves by bulk flow, the movement of a fluid driven by pressure.
• The transport of xylem sap involves transpiration, the loss of water vapor from a plant’s surface.
• Transpired water is replaced as water travels up from the roots.
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Pulling Xylem Sap: The Cohesion-Tension Hypothesis
• According to the cohesion-tension hypothesis, transpiration and water cohesion pull water from shoots to roots.
• Xylem sap is normally under negative pressure, or tension.
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Ascent of xylem sap
Water molecule
Water uptake from soil
Water
Soil particle
Root hair
Figure 29.18b
Cohesionby hydrogenbonding
Cohesionand adhesionin the xylem
Cell wall
Xylemcells
Adhesion by hydrogenbonding
Figure 29.18c
Transpiration
Water molecule
Xylem sap
Mesophyll cells
Stoma
Atmosphere
Figure 29.18
Cohesionby hydrogenbonding
Water molecule
Cohesionand adhesionin the xylem
Water uptake from soilWater
Soil particle
Root hair
Cell wall
Transpiration
Xylemcells
Water molecule
Adhesion by hydrogenbonding
Xylem sap
Mesophyll cells
Stoma
Atmosphere
Outside air
Wat
er p
ote
nti
al g
rad
ien
t
Leaf (air spaces)
Trunk xylem
Leaf (cell walls)
Trunk xylem
Soil
-7.0 MPa
-100.0 MPa=
=
-1.0 MPa=
−0.8 MPa
−0.6 MPa
−0.3 MPa
Integrating Chapter 29 (Pearson Web Page) – due Thursday 11:59 pm