Lecture 6 Water Relations

1
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• B. Properties of water
• C. Importance of water for organisms
• D. Water potential
• E. Osmoregulation

2
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• Polar molecule (positive and negative
  charges).
• B. Properties of water
• C. Importance of water for organisms
• D. Water potential
• E. Osmoregulation

3
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• Polar molecule (positive and negative
  charges). This causes H bonding between water
  molecules (cohesion) and attraction to other
  molecules and surfaces (adhesion).
• B. Properties of water
• C. Importance of water for organisms
• D. Water potential
• E. Osmoregulation

4
(No Transcript)
5
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• Polar molecule (positive and negative
  charges). This causes H bonding between water
  molecules (cohesion) and attraction to other
  molecules and surfaces (adhesion).
• B. Properties of water
• C. Importance of water for organisms
• D. Water potential
• E. Osmoregulation

6
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• Polar molecule (positive and negative
  charges). This causes H bonding between water
  molecules (cohesion) and attraction to other
  molecules and surfaces (adhesion).
• B. Properties of water
• 1. High melting and boiling point.
• C. Importance of water for organisms
• D. Water potential
• E. Osmoregulation

7
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• Polar molecule (positive and negative
  charges). This causes H bonding between water
  molecules (cohesion) and attraction to other
  molecules and surfaces (adhesion).
• B. Properties of water
• 1. High melting and boiling point. Water is
  liquid at ambient Earth temperatures.
• C. Importance of water for organisms
• D. Water potential
• E. Osmoregulation

8
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• Polar molecule (positive and negative
  charges). This causes H bonding between water
  molecules (cohesion) and attraction to other
  molecules and surfaces (adhesion).
• B. Properties of water
• 1. High melting and boiling point. Water is
  liquid at ambient Earth temperatures.
• 2. Water has high specific heat and thus
  helps maintain a fairly constant temperature
  in an organisms body.
• C. Importance of water for organisms
• D. Water potential
• E. Osmoregulation

9
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• Polar molecule (positive and negative
  charges). This causes H bonding between water
  molecules (cohesion) and attraction to other
  molecules and surfaces (adhesion).
• B. Properties of water
• 1. High melting and boiling point. Water is
  liquid at ambient Earth temperatures.
• 2. Water has high specific heat and thus
  helps maintain a fairly constant temperature
  in an organisms body.
• 3. Excellent solvent. Dissolves other polar
  substances.

10
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• Polar molecule (positive and negative
  charges). This causes H bonding between water
  molecules (cohesion) and attraction to other
  molecules and surfaces (adhesion).
• B. Properties of water
• 1. High melting and boiling point. Water is
  liquid at ambient Earth temperatures.
• 2. Water has high specific heat and thus
  helps maintain a fairly constant temperature
  in an organisms body.
• 3. Excellent solvent. Dissolves other polar
  substances.
• 4. Flows easily so is a good medium for
  transport of solutes.

11
Lecture 6 Water Relations

• I. Introduction
• A. Characteristics of the water molecule (FIG.
  1)
• Polar molecule (positive and negative
  charges). This causes H bonding between water
  molecules (cohesion) and attraction to other
  molecules and surfaces (adhesion).
• B. Properties of water
• 1. High melting and boiling point. Water is
  liquid at ambient Earth temperatures.
• 2. Water has high specific heat and thus
  helps maintain a fairly constant temperature
  in an organisms body.
• 3. Excellent solvent. Dissolves other polar
  substances.
• 4. Flows easily so is a good medium for
  transport of solutes.
• 5. Transparent so doesnt interfere with
  photosynthesis.

12
Lecture 6 Water Relations

• I. Introduction
• B. Properties of water
• 1. High melting and boiling point. Water is
  liquid at ambient Earth temperatures.
• 2. Water has high specific heat and thus
  helps maintain a fairly constant temperature
  in an organisms body.
• 3. Excellent solvent. Dissolves other polar
  substances.
• 4. Flows easily so is a good medium for
  transport of solutes.
• 5. Transparent so doesnt interfere with
  photosynthesis.
• C. Importance of water for organisms
• 1. Individuals -
• 2. Species -

13
Lecture 6 Water Relations

• I. Introduction
• B. Properties of water
• 1. High melting and boiling point. Water is
  liquid at ambient Earth temperatures.
• 2. Water has high specific heat and thus
  helps maintain a fairly constant temperature
  in an organisms body.
• 3. Excellent solvent. Dissolves other polar
  substances.
• 4. Flows easily so is a good medium for
  transport of solutes.
• 5. Transparent so doesnt interfere with
  photosynthesis.
• C. Importance of water for organisms
• 1. Individuals - most cells organisms
  contain 70 - 95 water.
• 2. Species -

14
Lecture 6 Water Relations

• I. Introduction
• B. Properties of water
• 1. High melting and boiling point. Water is
  liquid at ambient Earth temperatures.
• 2. Water has high specific heat and thus
  helps maintain a fairly constant temperature
  in an organisms body.
• 3. Excellent solvent. Dissolves other polar
  substances.
• 4. Flows easily so is a good medium for
  transport of solutes.
• 5. Transparent so doesnt interfere with
  photosynthesis.
• C. Importance of water for organisms
• 1. Individuals - most cells organisms
  contain 70 - 95 water.
• 2. Species - distributions often limited by
  water availability.

15
Lecture 6 Water Relations

• I. Introduction
• C. Importance of water for organisms
• 1. Individuals - most cells organisms
  contain 70 - 95 water.
• 2. Species - distributions often limited by
  water availability.
• D. Water potential
• 1. What is water potential?
• 2. The basic rule of water potential
• 3. Components of water potential

16
Lecture 6 Water Relations

• I. Introduction
• C. Importance of water for organisms
• 1. Individuals - most cells organisms
  contain 70 - 95 water.
• 2. Species - distributions often limited by
  water availability.
• D. Water potential
• 1. What is water potential? The free energy
  of water in a system.
• 2. The basic rule of water potential
• 3. Components of water potential

17
Lecture 6 Water Relations

• I. Introduction
• C. Importance of water for organisms
• 1. Individuals - most cells organisms
  contain 70 - 95 water.
• 2. Species - distributions often limited by
  water availability.
• D. Water potential
• 1. What is water potential? The free energy
  of water in a system. Measured in
  MegaPascals (MPa) or bars (10 bars 1 MPa).
• 2. The basic rule of water potential
• 3. Components of water potential

18
Lecture 6 Water Relations

• I. Introduction
• C. Importance of water for organisms
• 1. Individuals - most cells organisms
  contain 70 - 95 water.
• 2. Species - distributions often limited by
  water availability.
• D. Water potential
• 1. What is water potential? The free energy
  of water in a system. Measured in
  MegaPascals (MPa) or bars (10 bars 1 MPa).
• 2. The basic rule of water potential. Water
  flows spontaneously from areas of high water
  potential to low water potential in a system.
• 3. Components of water potential

19
Lecture 6 Water Relations

• I. Introduction
• C. Importance of water for organisms
• 1. Individuals - most cells organisms
  contain 70 - 95 water.
• 2. Species - distributions often limited by
  water availability.
• D. Water potential
• 1. What is water potential? The free energy
  of water in a system. Measured in
  MegaPascals (MPa) or bars (10 bars 1 MPa).
• 2. The basic rule of water potential. Water
  flows spontaneously from areas of high water
  potential to low water potential in a system.
• 3. Components of water potential.
• ? ?g ?p ?p ?t

20
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 1. What is water potential? The free energy
  of water in a system. Measured in
  MegaPascals (MPa) or bars (10 bars 1 MPa).
• 2. The basic rule of water potential. Water
  flows spontaneously from areas of high water
  potential to low water potential in a system.
• 3. Components of water potential.
• ? ?g ?p ?p ?t where g
• p
• p
• t

21
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 1. What is water potential? The free energy
  of water in a system. Measured in
  MegaPascals (MPa) or bars (10 bars 1 MPa).
• 2. The basic rule of water potential. Water
  flows spontaneously from areas of high water
  potential to low water potential in a system.
• 3. Components of water potential.
• ? ?g ?p ?p ?t where g
  gravity
• p p
• t

22
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 1. What is water potential? The free energy
  of water in a system. Measured in
  MegaPascals (MPa) or bars (10 bars 1 MPa).
• 2. The basic rule of water potential. Water
  flows spontaneously from areas of high water
  potential to low water potential in a system.
• 3. Components of water potential.
• ? ?g ?p ?p ?t where g
  gravity
• p pressure
• p
• t

23
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 1. What is water potential? The free energy
  of water in a system. Measured in
  MegaPascals (MPa) or bars (10 bars 1 MPa).
• 2. The basic rule of water potential. Water
  flows spontaneously from areas of high water
  potential to low water potential in a system.
• 3. Components of water potential.
• ? ?g ?p ?p ?t where g
  gravity
• p pressure
• p solute concentration
  t

24
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 1. What is water potential? The free energy
  of water in a system. Measured in
  MegaPascals (MPa) or bars (10 bars 1 MPa).
• 2. The basic rule of water potential. Water
  flows spontaneously from areas of high water
  potential to low water potential in a system.
• 3. Components of water potential.
• ? ?g ?p ?p ?t where g
  gravity
• p pressure
• p solute concentration
• t attraction to surfaces

25
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 3. Components of water potential.
• ? ?g ?p ?p ?t where g
  gravity
• p pressure
• p solute concentration
• t attraction to surfaces
  ?g gravitational potential
• ?p pressure potential
• ?p osmotic potential (due to
  solutes)
• ?t matric potential (due to
  surfaces)

26
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 3. Components of water potential.
• ? ?g ?p ?p ?t
• ?g gravitational potential
• ?p pressure potential
• ?p osmotic potential (due to
  solutes)
• ?t matric potential (due to surfaces).
• A system can be anything containing water
  stream, soil, cell, organism.

27
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 3. Components of water potential.
• ? ?g ?p ?p ?t
• A system can be anything containing water
  stream, soil, cell, organism.
• Same rules of water potential apply in all
  systems but components vary.

28
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 3. Components of water potential.
• ? ?g ?p ?p ?t
• A system can be anything containing water
  stream, soil, cell, organism.
• Same rules of water potential apply in all
  systems but components vary.
• Stream
• Soil
• Cell
• Organism

29
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 3. Components of water potential.
• ? ?g ?p ?p ?t
• A system can be anything containing water
  stream, soil, cell, organism.
• Same rules of water potential apply in all
  systems but components vary.
• Stream ?g
• Soil
• Cell -
• Organism -

30
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 3. Components of water potential.
• ? ?g ?p ?p ?t
• A system can be anything containing water
  stream, soil, cell, organism.
• Same rules of water potential apply in all
  systems but components vary.
• Stream ?g
• Soil ?g ?t ?p
• Cell
• Organism

31
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 3. Components of water potential.
• ? ?g ?p ?p ?t
• A system can be anything containing water
  stream, soil, cell, organism.
• Same rules of water potential apply in all
  systems but components vary.
• Stream ?g
• Soil ?g ?t ?p
• Cell ?p ?t ?p (?p primarily in plants)
• Organism

32
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• 3. Components of water potential.
• ? ?g ?p ?p ?t
• A system can be anything containing water
  stream, soil, cell, organism.
• Same rules of water potential apply in all
  systems but components vary.
• Stream ?g
• Soil ?g ?t ?p
• Cell ?p ?t ?p (?p primarily in plants)
• Organism ?g ?p ?p ?t (depends on organism)

33
Lecture 6 Water Relations

• I. Introduction
• D. Water potential
• Stream ?g
• Soil ?g ?t ?p
• Cell ?p ?t ?p (?p primarily in plants)
• Organism ?g ?p ?p ?t (depends on
  organism)
• E. Osmoregulation
• 1. What is osmoregulation?
• 2. Types of organisms

34
Lecture 6 Water Relations

• I. Introduction
• E. Osmoregulation
• 1. What is osmoregulation? Relates only to
  living systems like cells or organisms, not
  physical systems like a stream or soil.
• 2. Types of organisms

35
Lecture 6 Water Relations

• I. Introduction
• E. Osmoregulation
• 1. What is osmoregulation? Relates only to
  living systems like cells or organisms, not
  physical systems like a stream or soil.
  Maintaining proper solute concentration to
  regulate water gain and loss.
• 2. Types of organisms

36
Lecture 6 Water Relations

• I. Introduction
• E. Osmoregulation
• 1. What is osmoregulation? Relates only to
  living systems like cells or organisms, not
  physical systems like a stream or soil.
  Maintaining proper solute concentration to
  regulate water gain and loss.
• 2. Types of organisms
• a. Isotonic -
• b. Hypertonic -
• c. Hypotonic -

37
Lecture 6 Water Relations

• I. Introduction
• E. Osmoregulation
• 1. What is osmoregulation? Relates only to
  living systems like cells or organisms, not
  physical systems like a stream or soil.
  Maintaining proper solute concentration to
  regulate water gain and loss.
• 2. Types of organisms
• a. Isotonic - solute concentration inside
  organism solute concentration in
  surrounding environment.
• b. Hypertonic -
• c. Hypotonic -

38
Lecture 6 Water Relations

• I. Introduction
• E. Osmoregulation
• 1. What is osmoregulation? Relates only to
  living systems like cells or organisms, not
  physical systems like a stream or soil.
  Maintaining proper solute concentration to
  regulate water gain and loss.
• 2. Types of organisms
• a. Isotonic - solute concentration inside
  organism solute concentration in
  surrounding environment. Most marine
  invertebrates (e.g. seastars, anemones).
• b. Hypertonic -
• c. Hypotonic -

39
Lecture 6 Water Relations

• I. Introduction
• E. Osmoregulation
• 2. Types of organisms
• a. Isotonic - solute concentration inside
  organism solute concentration in
  surrounding environment. Most marine
  invertebrates (e.g. seastars, anemones).
• b. Hypertonic - solute concentration
  inside organism gt solute concentration
  in surrounding environment.
• c. Hypotonic -

40
Lecture 6 Water Relations

• I. Introduction
• E. Osmoregulation
• 2. Types of organisms
• a. Isotonic - solute concentration inside
  organism solute concentration in
  surrounding environment. Most marine
  invertebrates (e.g. seastars, anemones).
• b. Hypertonic - solute concentration
  inside organism gt solute concentration
  in surrounding environment. Freshwater
  organisms most plants and fungi.
• c. Hypotonic -

41
Lecture 6 Water Relations

• I. Introduction
• E. Osmoregulation
• 2. Types of organisms
• a. Isotonic - solute concentration inside
  organism solute concentration in
  surrounding environment. Most marine
  invertebrates (e.g. seastars, anemones).
• b. Hypertonic - solute concentration
  inside organism gt solute concentration
  in surrounding environment. Freshwater
  organisms most plants and fungi.
• c. Hypotonic - solute concentration
  inside organism lt solute concentration
  in surrounding environment.

42
Lecture 6 Water Relations

• I. Introduction
• E. Osmoregulation
• 2. Types of organisms
• a. Isotonic - solute concentration inside
  organism solute concentration in
  surrounding environment. Most marine
  invertebrates (e.g. seastars, anemones).
• b. Hypertonic - solute concentration
  inside organism gt solute concentration
  in surrounding environment. Freshwater
  organisms most plants and fungi.
• c. Hypotonic - solute concentration
  inside organism lt solute concentration
  in surrounding environment. Marine vertebrates,
  some plants.

43
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• B. Gas exchange
• C. Water use efficiency (WUE)
• D. Alternative photosynthetic pathways

44
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability.
  Water availability depends largely on the type of
  soil a plant is growing in (FIG. 2)
• B. Gas exchange
• C. Water use efficiency (WUE)
• D. Alternative photosynthetic pathways

45
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46
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes
• 2. Xerophytes
• 3. Hydrophytes
• 4. Halophytes

47
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes - normal water requirements.
  Most plants, including typical garden
  plants.
• 2. Xerophytes
• 3. Hydrophytes
• 4. Halophytes

48
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes - normal water requirements.
  Most plants, including typical garden
  plants.
• 2. Xerophytes - plants of dry (xeric)
  environments having low water requirements.
  
• 3. Hydrophytes
• 4. Halophytes

49
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes - normal water requirements.
  Most plants, including typical garden
  plants.
• 2. Xerophytes - plants of dry (xeric)
  environments having low water requirements.
  Ex cacti, typical desert plants.
• 3. Hydrophytes
• 4. Halophytes

50
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes - normal water requirements.
  Most plants, including typical garden
  plants.
• 2. Xerophytes - plants of dry (xeric)
  environments having low water requirements.
  Ex cacti, typical desert plants.
• 3. Hydrophytes - plants needing abundant
  water.
• 4. Halophytes

51
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes - normal water requirements.
  Most plants, including typical garden
  plants.
• 2. Xerophytes - plants of dry (xeric)
  environments having low water requirements.
  Ex cacti, typical desert plants.
• 3. Hydrophytes - plants needing abundant
  water. Ex water lilies.
• 4. Halophytes

52
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes - normal water requirements.
  Most plants, including typical garden
  plants.
• 2. Xerophytes - plants of dry (xeric)
  environments having low water requirements.
  Ex cacti, typical desert plants.
• 3. Hydrophytes - plants needing abundant
  water. Ex water lilies.
• 4. Halophytes - plants that tolerate saline
  soils.

53
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes - normal water requirements.
  Most plants, including typical garden
  plants.
• 2. Xerophytes - plants of dry (xeric)
  environments having low water requirements.
  Ex cacti, typical desert plants.
• 3. Hydrophytes - plants needing abundant
  water. Ex water lilies.
• 4. Halophytes - plants that tolerate saline
  soils. Ex saltbush (Atriplex species), ice
  plant (Mesembryanthemum)

54
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes - normal water requirements.
  Most plants, including typical garden
  plants.
• 2. Xerophytes - plants of dry (xeric)
  environments having low water requirements.
  Ex cacti, typical desert plants.
• 3. Hydrophytes - plants needing abundant
  water. Ex water lilies.
• 4. Halophytes - plants that tolerate saline
  soils. Ex saltbush (Atriplex species), ice
  plant (Mesembryanthemum). These plants produce
  excess solutes, store water, secrete salt from
  leaves, or keep salt out of roots.

55
Lecture 6 Water Relations

• II. Water Balance in Plants
• A. Plant adaptations to water availability (FIG.
  2)
• 1. Mesophytes - normal water requirements.
  Most plants, including typical garden
  plants.
• 2. Xerophytes - plants of dry (xeric)
  environments having low water requirements.
  Ex cacti, typical desert plants.
• 3. Hydrophytes - plants needing abundant
  water. Ex water lilies.
• 4. Halophytes - plants that tolerate saline
  soils. Ex saltbush (Atriplex species), ice
  plant (Mesembryanthemum). These plants produce
  excess solutes, store water, secrete salt from
  leaves, or keep salt out of roots.
• B. Gas exchange

56
Lecture 6 Water Relations

• II. Water Balance in Plants
• B. Gas exchange. Diffusion of ___ into a leaf
  and ___ and ___ out of the leaf
  when stomata are open.

57
Lecture 6 Water Relations

• II. Water Balance in Plants
• B. Gas exchange. Diffusion of CO2 into a leaf
  and O2 and H2O out of the leaf
  when stomata are open.

58
Lecture 6 Water Relations

• II. Water Balance in Plants
• B. Gas exchange. Diffusion of CO2 into a leaf
  and O2 and H2O out of the leaf
  when stomata are open. Thus water loss through
  transpiration is an inevitable consequence of
  photosynthesis.

59
Lecture 6 Water Relations

• II. Water Balance in Plants
• B. Gas exchange. Diffusion of CO2 into a leaf
  and O2 and H2O out of the leaf
  when stomata are open. Thus water loss through
  transpiration is an inevitable consequence of
  photosynthesis.
• C. Water use efficiency (WUE)

60
Lecture 6 Water Relations

• II. Water Balance in Plants
• B. Gas exchange. Diffusion of CO2 into a leaf
  and O2 and H2O out of the leaf
  when stomata are open. Thus water loss through
  transpiration is an inevitable consequence of
  photosynthesis.
• C. Water use efficiency (WUE). The amount of
  CO2 entering the leaf compared to the amount of
  water lost.

61
Lecture 6 Water Relations

• II. Water Balance in Plants
• B. Gas exchange. Diffusion of CO2 into a leaf
  and O2 and H2O out of the leaf
  when stomata are open. Thus water loss through
  transpiration is an inevitable consequence of
  photosynthesis.
• C. Water use efficiency (WUE). The amount of
  CO2 entering the leaf compared to the amount of
  water lost. High WUE means little loss of water
  when taking up CO2. High WUE is essential in
  deserts!

62
Lecture 6 Water Relations

• II. Water Balance in Plants
• B. Gas exchange. Diffusion of CO2 into a leaf
  and O2 and H2O out of the leaf
  when stomata are open. Thus water loss through
  transpiration is an inevitable consequence of
  photosynthesis.
• C. Water use efficiency (WUE). The amount of
  CO2 entering the leaf compared to the amount of
  water lost. High WUE means little loss of water
  when taking up CO2. High WUE is essential in
  deserts!
• D. Alternative photosynthetic pathways
• 1. C3 (LEC. 5, FIG. 6)
• 2. C4 (FIG. 3)
• 3. CAM (FIG. 4)

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64
Lecture 6 Water Relations

• II. Water Balance in Plants
• C. Water use efficiency (WUE). The amount of
  CO2 entering the leaf compared to the amount of
  water lost. High WUE means little loss of water
  when taking up CO2. High WUE is essential in
  deserts!
• D. Alternative photosynthetic pathways
• 1. C3 (LEC. 5, FIG. 6). The critical enzyme
  in the Calvin cycle, rubisco, is not very
  efficient. It has an affinity for O2 as well as
  CO2. This is called photorespiration and
  results in low WUE.

65
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66
Lecture 6 Water Relations

• II. Water Balance in Plants
• C. Water use efficiency (WUE). The amount of
  CO2 entering the leaf compared to the amount of
  water lost. High WUE means little loss of water
  when taking up CO2. High WUE is essential in
  deserts!
• D. Alternative photosynthetic pathways
• 1. C3 (LEC. 5, FIG. 6). The critical enzyme
  in the Calvin cycle, rubisco, is not very
  efficient. It has an affinity for O2 as well as
  CO2. This is called photorespiration and
  results in low WUE. However, the majority
  of plants are C3, including all trees and
  most shrubs and herbaceous plants.

67
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 1. C3 (LEC. 5, FIG. 6). The critical enzyme
  in the Calvin cycle, rubisco, is not very
  efficient. It has an affinity for O2 as well as
  CO2. This is called photorespiration and
  results in low WUE. However, the majority
  of plants are C3, including all trees and
  most shrubs and herbaceous plants.
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• a. What is the C4 pathway?
• b. Advantage
• c. Trade-off
• d. Examples

68
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 1. C3 (LEC. 5, FIG. 6). The critical enzyme
  in the Calvin cycle, rubisco, is not very
  efficient. It has an affinity for O2 as well as
  CO2. This is called photorespiration and
  results in low WUE. However, the majority
  of plants are C3, including all trees and
  most shrubs and herbaceous plants.
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• a. What is the C4 pathway? CO2 is first
  fixed (C attached to substrate) by PEP
  carboxylase and then transported to interior
  cells as a 4-carbon acid and released in
  high-CO2 environment.

69
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70
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 1. C3 (LEC. 5, FIG. 6). The critical enzyme
  in the Calvin cycle, rubisco, is not very
  efficient. It has an affinity for O2 as well as
  CO2. This is called photorespiration and
  results in low WUE. However, the majority
  of plants are C3, including all trees and
  most shrubs and herbaceous plants.
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• a. What is the C4 pathway? CO2 is first
  fixed (C attached to substrate) by PEP
  carboxylase and then transported to interior
  cells as a 4-carbon acid and released in
  high-CO2 environment. The CO2 is then
  fixed by rubisco in the normal Calvin cycle.

71
(No Transcript)
72
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• a. What is the C4 pathway? CO2 is first
  fixed (C attached to substrate) by PEP
  carboxylase and then transported to interior
  cells as a 4-carbon acid and released in
  high-CO2 environment. The CO2 is then
  fixed by rubisco in the normal Calvin cycle.
• b. Advantage

73
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• a. What is the C4 pathway? CO2 is first
  fixed (C attached to substrate) by PEP
  carboxylase and then transported to interior
  cells as a 4-carbon acid and released in
  high-CO2 environment. The CO2 is then
  fixed by rubisco in the normal Calvin cycle.
• b. Advantage. High CO2 environment means
  higher WUE and less water loss.

74
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• a. What is the C4 pathway? CO2 is first
  fixed (C attached to substrate) by PEP
  carboxylase and then transported to interior
  cells as a 4-carbon acid and released in
  high-CO2 environment. The CO2 is then
  fixed by rubisco in the normal Calvin cycle.
• b. Advantage. High CO2 environment means
  higher WUE and less water loss.
• c. Trade-off

75
(No Transcript)
76
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• a. What is the C4 pathway? CO2 is first
  fixed (C attached to substrate) by PEP
  carboxylase and then transported to interior
  cells as a 4-carbon acid and released in
  high-CO2 environment. The CO2 is then
  fixed by rubisco in the normal Calvin cycle.
• b. Advantage. High CO2 environment means
  higher WUE and less water loss.
• c. Trade-off. More energy required so
  best in high-light, warm environments.

77
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• a. What is the C4 pathway? CO2 is first
  fixed (C attached to substrate) by PEP
  carboxylase and then transported to interior
  cells as a 4-carbon acid and released in
  high-CO2 environment. The CO2 is then
  fixed by rubisco in the normal Calvin cycle.
• b. Advantage. High CO2 environment means
  higher WUE and less water loss.
• c. Trade-off. More energy required so
  best in high-light, warm environments.
  Examples corn, sugar cane, saltbush,
  tumbleweed, crabgrass, many other grasses.

78
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• c. Trade-off. More energy required so
  best in high-light, warm environments.
  Examples corn, sugar cane, saltbush,
  tumbleweed, crabgrass, many other grasses.
• 3. CAM (FIG. 4) CAM Crassulacean acid
  metabolism

79
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• c. Trade-off. More energy required so
  best in high-light, warm environments.
  Examples corn, sugar cane, saltbush,
  tumbleweed, crabgrass, many other grasses.
• 3. CAM (FIG. 4) CAM Crassulacean acid
  metabolism
• a. What is the CAM pathway?
• b. Advantage
• c. Trade-off
• d. Examples

80
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• c. Trade-off. More energy required so
  best in high-light, warm environments.
  Examples corn, sugar cane, saltbush,
  tumbleweed, crabgrass, many other grasses.
• 3. CAM (FIG. 4) CAM Crassulacean acid
  metabolism
• a. What is the CAM pathway? Stomata open
  at night to take in CO2. CO2 fixed by
  PEP carboxylase and stored as malic acid
  in vacuoles. Then CO2 released during day into
  chloroplasts for use in Calvin cycle.
  Stomata are closed during the day.
• b. Advantage
• c. Trade-off
• d. Examples

81
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82
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 2. C4 (Hatch-Slack pathway)(FIG. 3)
• c. Trade-off. More energy required so
  best in high-light, warm environments.
  Examples corn, sugar cane, saltbush,
  tumbleweed, crabgrass, many other grasses.
• 3. CAM (FIG. 4) CAM Crassulacean acid
  metabolism
• a. What is the CAM pathway? Stomata open
  at night to take in CO2. CO2 fixed by
  PEP carboxylase and stored as malic acid
  in vacuoles. Then CO2 released during day into
  chloroplasts for use in Calvin cycle.
  Stomata are closed during the day.
• b. Advantage
• c. Trade-off
• d. Examples

83
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 3. CAM (FIG. 4) CAM Crassulacean acid
  metabolism
• a. What is the CAM pathway? Stomata open
  at night to take in CO2. CO2 fixed by
  PEP carboxylase and stored as malic acid
  in vacuoles. Then CO2 released during day into
  chloroplasts for use in Calvin cycle.
  Stomata are closed during the day.
• b. Advantage. Much higher WUE because
  very little water lost through stomata
  at night.
• c. Trade-off
• d. Examples

84
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 3. CAM (FIG. 4) CAM Crassulacean acid
  metabolism
• a. What is the CAM pathway? Stomata open
  at night to take in CO2. CO2 fixed by
  PEP carboxylase and stored as malic acid
  in vacuoles. Then CO2 released during day into
  chloroplasts for use in Calvin cycle.
  Stomata are closed during the day.
• b. Advantage. Much higher WUE because
  very little water lost through stomata
  at night.
• c. Trade-off. More energy required and
  acid builds up in cells.
• d. Examples

85
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 3. CAM (FIG. 4) CAM Crassulacean acid
  metabolism
• a. What is the CAM pathway? Stomata open
  at night to take in CO2. CO2 fixed by
  PEP carboxylase and stored as malic acid
  in vacuoles. Then CO2 released during day into
  chloroplasts for use in Calvin cycle.
  Stomata are closed during the day.
• b. Advantage. Much higher WUE because
  very little water lost through stomata
  at night.
• c. Trade-off. More energy required and
  acid builds up in cells.
• d. Examples cacti (Cactaceae),
  stonecrops (Crassulaceae), euphorbias
  (Euphorbiaceae), Agave.

86
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 3. CAM (FIG. 4) CAM Crassulacean acid
  metabolism
• c. Trade-off. More energy required and
  acid builds up in cells.
• d. Examples cacti (Cactaceae),
  stonecrops (Crassulaceae), euphorbias
  (Euphorbiaceae), Agave.
• 4. Photosynthesis rates of different pathways
  (FIG. 5)

87
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88
Lecture 6 Water Relations

• II. Water Balance in Plants
• D. Alternative photosynthetic pathways
• 3. CAM (FIG. 4) CAM Crassulacean acid
  metabolism
• c. Trade-off. More energy required and
  acid builds up in cells.
• d. Examples cacti (Cactaceae),
  stonecrops (Crassulaceae), euphorbias
  (Euphorbiaceae), Agave.
• 4. Photosynthesis rates of different pathways
  (FIG. 5)
• Heliophytes shade-intolerant
• Sciophytes shade-tolerant
• CAM plants photosynthesis rates are below
  sciophytes

89
Lecture 6 Water Relations

• III. Water Balance in Animals
• A. Water gain by terrestrial animals
• B. Water loss by terrestrial animals
• C. Adaptations in arid regions
• D. Osmoregulation in aquatic animals (FIG. 7)
• E. Other mechanisms for osmoregulation

90
Lecture 6 Water Relations

• III. Water Balance in Animals
• A. Water gain by terrestrial animals
• Primarily from drinking and eating.
• B. Water loss by terrestrial animals

91
Lecture 6 Water Relations

• III. Water Balance in Animals
• A. Water gain by terrestrial animals
• Primarily from drinking and eating.
• B. Water loss by terrestrial animals
• Urine (chemical wastes, especially nitrogenous
  wastes)

92
Lecture 6 Water Relations

• III. Water Balance in Animals
• A. Water gain by terrestrial animals
• Primarily from drinking and eating.
• B. Water loss by terrestrial animals
• Urine (chemical wastes, especially nitrogenous
  wastes)
• Feces (solid wastes)

93
Lecture 6 Water Relations

• III. Water Balance in Animals
• A. Water gain by terrestrial animals
• Primarily from drinking and eating.
• B. Water loss by terrestrial animals
• Urine (chemical wastes, especially nitrogenous
  wastes)
• Feces (solid wastes)
• Evaporation from skin and lungs (respiration)

94
Lecture 6 Water Relations

• III. Water Balance in Animals
• A. Water gain by terrestrial animals
• Primarily from drinking and eating.
• B. Water loss by terrestrial animals
• Urine (chemical wastes, especially nitrogenous
  wastes)
• Feces (solid wastes)
• Evaporation from skin and lungs (respiration)
• C. Adaptations in arid regions

95
Lecture 6 Water Relations

• III. Water Balance in Animals
• A. Water gain by terrestrial animals
• Primarily from drinking and eating.
• B. Water loss by terrestrial animals
• Urine (chemical wastes, especially nitrogenous
  wastes)
• Feces (solid wastes)
• Evaporation from skin and lungs (respiration)
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• 2. Reduce water loss (FIG. 6)
• 3. Tolerate dehydration

96
Lecture 6 Water Relations

• III. Water Balance in Animals
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• a. Migrate out during dry seasons
• b.
• c.
• 2. Reduce water loss (FIG. 6)
• 3. Tolerate dehydration

97
Lecture 6 Water Relations

• III. Water Balance in Animals
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• a. Migrate out during dry seasons.
  Examples large African ungulates like
  gazelles, wildebeest.
• b.
• c.
• 2. Reduce water loss (FIG. 6)
• 3. Tolerate dehydration

98
Lecture 6 Water Relations

• III. Water Balance in Animals
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• a. Migrate out during dry seasons.
  Examples large African ungulates like
  gazelles, wildebeest.
• b. Go dormant during dry season
• c.
• 2. Reduce water loss (FIG. 6)
• 3. Tolerate dehydration

99
Lecture 6 Water Relations

• III. Water Balance in Animals
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• a. Migrate out during dry seasons.
  Examples large African ungulates like
  gazelles, wildebeest.
• b. Go dormant during dry season.
  Dormancy - desert plants.
• Diapause - insects. Estivation
  below ground - toads, snails, etc c.
• 2. Reduce water loss (FIG. 6)
• 3. Tolerate dehydration

100
Lecture 6 Water Relations

• III. Water Balance in Animals
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• a. Migrate out during dry seasons.
  Examples large African ungulates like
  gazelles, wildebeest.
• b. Go dormant during dry season.
  Dormancy - desert plants.
• Diapause - insects. Estivation
  below ground - toads, snails, etc c. Become
  nocturnal.
• 2. Reduce water loss (FIG. 6)
• 3. Tolerate dehydration

101
Lecture 6 Water Relations

• III. Water Balance in Animals
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• a. Migrate out during dry seasons.
  Examples large African ungulates like
  gazelles, wildebeest.
• b. Go dormant during dry season.
  Dormancy - desert plants.
• Diapause - insects. Estivation
  below ground - toads, snails, etc c. Become
  nocturnal. Desert rodents and other desert
  animals.
• 2. Reduce water loss (FIG. 6)
• 3. Tolerate dehydration

102
Lecture 6 Water Relations

• III. Water Balance in Animals
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• a. Migrate out during dry seasons.
  Examples large African ungulates like
  gazelles, wildebeest.
• b. Go dormant during dry season.
  Dormancy - desert plants.
• Diapause - insects. Estivation
  below ground - toads, snails, etc c. Become
  nocturnal. Desert rodents and other desert
  animals.
• 2. Reduce water loss (FIG. 6)
• a.
• b.

103
Lecture 6 Water Relations

• III. Water Balance in Animals
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• a. Migrate out during dry seasons.
  Examples large African ungulates like
  gazelles, wildebeest.
• b. Go dormant during dry season.
  Dormancy - desert plants.
• Diapause - insects. Estivation
  below ground - toads, snails, etc c. Become
  nocturnal. Desert rodents and other desert
  animals.
• 2. Reduce water loss (FIG. 6)
• a. Reabsorb water in intestine to reduce
  loss in urine feces.
• b.

104
Lecture 6 Water Relations

• III. Water Balance in Animals
• C. Adaptations in arid regions
• 1. Avoid adverse conditions
• a. Migrate out during dry seasons.
  Examples large African ungulates like
  gazelles, wildebeest.
• b. Go dormant during dry season.
  Dormancy - desert plants.
• Diapause - insects. Estivation
  below ground - toads, snails, etc c. Become
  nocturnal. Desert rodents and other desert
  animals.
• 2. Reduc