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Biology in Focus - Chapter 29

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Biology in Focus - Chapter 29

  1. 1. CAMPBELL BIOLOGY IN FOCUS © 2014 Pearson Education, Inc. Urry • Cain • Wasserman • Minorsky • Jackson • Reece Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge 29 Resource Acquisition, Nutrition, and Transport in Vascular Plants
  2. 2. Overview: Underground Plants  Stone plants (Lithops) are adapted to life in the desert  Two succulent leaf tips are exposed above ground; the rest of the plant lives below ground © 2014 Pearson Education, Inc.
  3. 3. © 2014 Pearson Education, Inc. Figure 29.1
  4. 4.  The success of plants depends on their ability to gather and conserve resources from their environment  The transport of materials is central to the integrated functioning of the whole plant © 2014 Pearson Education, Inc.
  5. 5. Concept 29.1: Adaptations for acquiring resources were key steps in the evolution of vascular plants  The evolution of adaptations enabling plants to acquire resources from both above and below ground sources allowed for the successful colonization of land by vascular plants © 2014 Pearson Education, Inc.
  6. 6.  The algal ancestors of land plants absorbed water, minerals, and CO2 directly from surrounding water  Early nonvascular land plants lived in shallow water and had aerial shoots  Natural selection favored taller plants with flat appendages, multicellular branching roots, and efficient transport © 2014 Pearson Education, Inc.
  7. 7.  The evolution of xylem and phloem in land plants made possible the development of extensive root and shoot systems that carry out long-distance transport  Xylem transports water and minerals from roots to shoots  Phloem transports photosynthetic products from sources to sinks © 2014 Pearson Education, Inc.
  8. 8. © 2014 Pearson Education, Inc. Figure 29.2-1 H2O and minerals H2O
  9. 9. © 2014 Pearson Education, Inc. Figure 29.2-2 H2O and minerals H2O O2 CO2 O2CO2
  10. 10. © 2014 Pearson Education, Inc. Figure 29.2-3 Light H2O and minerals H2O Sugar O2 CO2 O2CO2
  11. 11.  Adaptations in each species represent compromises between enhancing photosynthesis and minimizing water loss © 2014 Pearson Education, Inc.
  12. 12. Shoot Architecture and Light Capture  Stems serve as conduits for water and nutrients and as supporting structures for leaves  Shoot height and branching pattern affect light capture  There is a trade-off between growing tall and branching © 2014 Pearson Education, Inc.
  13. 13.  Phyllotaxy, the arrangement of leaves on a stem, is specific to each species  Most angiosperms have alternate phyllotaxy with leaves arranged in a spiral  The angle between leaves is 137.5° and likely minimizes shading of lower leaves © 2014 Pearson Education, Inc.
  14. 14. © 2014 Pearson Education, Inc. Figure 29.3 Shoot apical meristem Buds 34 21 42 29 16 11 19 27 3224 40 28 15 10 23 31 18 13 26 22 12 17 2520 1 2 3 4 5 6 7 8 9 14 1 mm
  15. 15. © 2014 Pearson Education, Inc. Figure 29.3a
  16. 16. © 2014 Pearson Education, Inc. Figure 29.3b Shoot apical meristem 34 21 42 29 16 11 19 27 3224 40 28 15 10 23 31 18 13 26 22 12 17 2520 1 2 3 4 5 6 7 8 9 14 1 mm
  17. 17.  The productivity of each plant is affected by the depth of the canopy, the leafy portion of all the plants in the community  Shedding of lower shaded leaves when they respire more than photosynthesize, self-pruning, occurs when the canopy is too thick © 2014 Pearson Education, Inc.
  18. 18.  Leaf orientation affects light absorption  In low-light conditions, horizontal leaves capture more sunlight  In sunny conditions, vertical leaves are less damaged by sun and allow light to reach lower leaves © 2014 Pearson Education, Inc.
  19. 19. Root Architecture and Acquisition of Water and Minerals  Soil is a resource mined by the root system  Root growth can adjust to local conditions  For example, roots branch more in a pocket of high nitrate than in a pocket of low nitrate  Roots are less competitive with other roots from the same plant than with roots from different plants © 2014 Pearson Education, Inc.
  20. 20.  Roots and the hyphae of soil fungi form mutualistic associations called mycorrhizae  Mutualisms with fungi helped plants colonize land  Mycorrhizal fungi increase the surface area for absorbing water and minerals © 2014 Pearson Education, Inc.
  21. 21. Concept 29.2: Different mechanisms transport substances over short or long distances  There are two major transport pathways through plants  The apoplast  The symplast © 2014 Pearson Education, Inc.
  22. 22. The Apoplast and Symplast: Transport Continuums  The apoplast consists of everything external to the plasma membrane  It includes cell walls, extracellular spaces, and the interior of vessel elements and tracheids  The symplast consists of the cytosol of the living cells in a plant, as well as the plasmodesmata © 2014 Pearson Education, Inc.
  23. 23.  Three transport routes for water and solutes are  The apoplastic route, through cell walls and extracellular spaces  The symplastic route, through the cytosol  The transmembrane route, across cell walls © 2014 Pearson Education, Inc.
  24. 24. © 2014 Pearson Education, Inc. Figure 29.4 Apoplastic route Cell wall Symplastic route Transmembrane route Cytosol Key Plasmodesma Plasma membrane Apoplast Symplast
  25. 25. Short-Distance Transport of Solutes Across Plasma Membranes  Plasma membrane permeability controls short- distance movement of substances  Both active and passive transport occur in plants  In plants, membrane potential is established through pumping H+ by proton pumps  In animals, membrane potential is established through pumping Na+ by sodium-potassium pumps © 2014 Pearson Education, Inc.
  26. 26. © 2014 Pearson Education, Inc. Figure 29.5 CYTOPLASM EXTRACELLULAR FLUID Proton pump Hydrogen ion Sucrose (neutral solute) Potassium ion Ion channel Nitrate (d) Ion channels(c) H+ and cotransport of ions (b) H+ and cotransport of neutral solutes (a) H+ and membrane potential H+ /sucrose cotransporter H+ /NO3 − cotransporter S NO3 − K+ K+ K+ K+ K+ K+ K+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ S S S S S H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+H+ H+ H+ H+ H+ NO3 − NO3 − NO3 − NO3 − NO3 −
  27. 27. © 2014 Pearson Education, Inc. Figure 29.5a CYTOPLASM EXTRACELLULAR FLUID Proton pump Hydrogen ion (a) H+ and membrane potential H+ H+ H+ H+ H+ H+ H+ H+
  28. 28. © 2014 Pearson Education, Inc. Figure 29.5b Sucrose (neutral solute) (b) H+ and cotransport of neutral solutes H+ /sucrose cotransporter S H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ S S S S S
  29. 29. © 2014 Pearson Education, Inc. Figure 29.5c 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 − NO3 −
  30. 30. © 2014 Pearson Education, Inc. Figure 29.5d Potassium ion Ion channel (d) Ion channels K+ K+ K+ K+ K+ K+ K+
  31. 31.  Plant cells use the energy of H+ gradients to cotransport other solutes by active transport © 2014 Pearson Education, Inc.
  32. 32.  Plant cell membranes have ion channels that allow only certain ions to pass © 2014 Pearson Education, Inc.
  33. 33. 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.
  34. 34.  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.
  35. 35.  Water potential is abbreviated as Ψ and measured in a unit of pressure called the megapascal (MPa)  Ψ = 0 MPa for pure water at sea level and at room temperature © 2014 Pearson Education, Inc.
  36. 36. How Solutes and Pressure Affect Water Potential  Both pressure and solute concentration affect water potential  This is expressed by the water potential equation: Ψ = ΨS + ΨP  The solute potential (ΨS) of a solution is directly proportional to its molarity  Solute potential is also called osmotic potential © 2014 Pearson Education, Inc.
  37. 37.  Pressure potential (ΨP) is the physical pressure on a solution  Turgor pressure is the pressure exerted by the plasma membrane against the cell wall, and the cell wall against the protoplast  The protoplast is the living part of the cell, which also includes the plasma membrane © 2014 Pearson Education, Inc.
  38. 38.  Water potential affects uptake and loss of water by plant cells  If a flaccid (limp) cell is placed in an environment with a higher solute concentration, the cell will lose water and undergo plasmolysis  Plasmolysis occurs when the protoplast shrinks and pulls away from the cell wall Water Movement Across Plant Cell Membranes © 2014 Pearson Education, Inc.
  39. 39. © 2014 Pearson Education, Inc. Figure 29.6 Plasmolyzed cell at osmotic equilibrium with its surroundings Turgid cell at osmotic equilibrium with its surroundings 0.4 M sucrose solution: (a) Initial conditions: cellular ψ > environmental ψ −0.9 MPa=ψ 0 MPa=ψ Initial flaccid cell: 0 MPa=ψ 0 0 = = ψP ψS Pure water: (b) Initial conditions: cellular ψ < environmental ψ −0.7 MPa=ψ −0.7 = = ψP ψS −0.9 = = ψP ψS 0 −0.9 MPa=ψ −0.9 = = ψP ψS 0 0 0.7= = ψP ψS −0.7
  40. 40. © 2014 Pearson Education, Inc. −0.9 Figure 29.6a Plasmolyzed cell at osmotic equilibrium with its surroundings 0.4 M sucrose solution: (a) Initial conditions: cellular ψ > environmental ψ −0.9 MPa=ψ −0.9 = = ψP ψS Initial flaccid cell: −0.9 MPa=ψ = = ψP ψS −0.7 MPa=ψ −0.7 = = ψP ψS 0 0 0
  41. 41. © 2014 Pearson Education, Inc. −0.7 Figure 29.6b Initial flaccid cell: −0.7 MPa=ψ = = ψP ψS Turgid cell at osmotic equilibrium with its surroundings Pure water: (b) Initial conditions: cellular ψ < environmental ψ 0 MPa=ψ 0 0 = = ψP ψS 0 MPa=ψ 0.7= = ψP ψS 0 −0.7
  42. 42.  If a flaccid cell is placed in a solution with a lower solute concentration, the cell will gain water and become turgid (firm)  Turgor loss in plants causes wilting, which can be reversed when the plant is watered © 2014 Pearson Education, Inc. Video: Turgid Elodea
  43. 43. © 2014 Pearson Education, Inc. Figure 29.7 Turgid Wilted
  44. 44. © 2014 Pearson Education, Inc. Figure 29.7a Wilted
  45. 45. © 2014 Pearson Education, Inc. Figure 29.7b Turgid
  46. 46. Aquaporins: Facilitating Diffusion of Water  Aquaporins are transport proteins in the cell membrane that allow the passage of water  These affect the rate of water movement across the membrane © 2014 Pearson Education, Inc.
  47. 47. Long-Distance Transport: The Role of Bulk Flow  Efficient long-distance transport of fluid requires bulk flow, the movement of a fluid driven by pressure  Water and solutes move together through tracheids and vessel elements of xylem and sieve-tube elements of phloem  Efficient movement is possible because mature tracheids and vessel elements have no cytoplasm, and sieve-tube elements have few organelles in their cytoplasm © 2014 Pearson Education, Inc.
  48. 48. Concept 29.3: Plants roots absorb essential elements from the soil  Water, air, and soil minerals contribute to plant growth  80–90% of a plant's fresh mass is water  96% of plant's dry mass consists of carbohydrates from the CO2 assimilated during photosynthesis  4% of a plant's dry mass is inorganic substances from soil © 2014 Pearson Education, Inc.
  49. 49. Macronutrients and Micronutrients  More than 50 chemical elements have been identified among the inorganic substances in plants, but not all of these are essential to plants  There are 17 essential elements, chemical elements required for a plant to complete its life cycle  Researchers use hydroponic culture, the growth of plants in mineral solutions, to determine which chemical elements are essential © 2014 Pearson Education, Inc.
  50. 50. © 2014 Pearson Education, Inc. Figure 29.8 Technique Control: Solution containing all minerals Experimental: Solution without potassium
  51. 51. © 2014 Pearson Education, Inc. Table 29.1
  52. 52.  Nine of the essential elements are called macronutrients because plants require them in relatively large amounts  The macronutrients are carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium © 2014 Pearson Education, Inc.
  53. 53.  The remaining eight are called micronutrients because plants need them in very small amounts  The micronutrients are chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum  Plants with C4 and CAM photosynthetic pathways also need sodium  Micronutrients function as cofactors, nonprotein helpers in enzymatic reactions © 2014 Pearson Education, Inc.
  54. 54. Symptoms of Mineral Deficiency  Symptoms of mineral deficiency depend on the nutrient's function and mobility within the plant  Deficiency of a mobile nutrient usually affects older organs more than young ones  Deficiency of a less mobile nutrient usually affects younger organs more than older ones  The most common deficiencies are those of nitrogen, potassium, and phosphorus © 2014 Pearson Education, Inc.
  55. 55. © 2014 Pearson Education, Inc. Figure 29.9 Nitrogen-deficient Potassium-deficient Phosphate-deficient Healthy
  56. 56. Soil Management  Ancient farmers recognized that crop yields would decrease on a particular plot over the years  Soil management, by fertilization and other practices, allowed for agriculture and cities © 2014 Pearson Education, Inc.
  57. 57. Fertilization  In natural ecosystems, nutrients are recycled through decomposition of feces and humus, dead organic material  Soils can become depleted of nutrients as plants and the nutrients they contain are harvested  Fertilization replaces mineral nutrients that have been lost from the soil © 2014 Pearson Education, Inc.
  58. 58.  Commercial fertilizers are enriched in nitrogen (N), phosphorus (P), and potassium (K)  Excess minerals are often leached from the soil and can cause algal blooms in lakes  Organic fertilizers are composed of manure, fishmeal, or compost  They release N, P, and K as they decompose © 2014 Pearson Education, Inc.
  59. 59. Adjusting Soil pH  Soil pH affects cation exchange and the chemical form of minerals  Cations are more available in slightly acidic soil, as H+ ions displace mineral cations from clay particles  The availability of different minerals varies with pH  For example, at pH 8 plants can absorb calcium but not iron © 2014 Pearson Education, Inc.
  60. 60.  At present, 30% of the world's farmland has reduced productivity because of soil mismanagement © 2014 Pearson Education, Inc.
  61. 61. The Living, Complex Ecosystem of Soil  Plants obtain most of their mineral nutrients from the topsoil  The basic physical properties of soil are  Texture  Composition © 2014 Pearson Education, Inc.
  62. 62. Soil Texture  Soil particles are classified by size; from largest to smallest they are called sand, silt, and clay  Topsoil is formed when mineral particles released from weathered rock mix with living organisms and humus © 2014 Pearson Education, Inc.
  63. 63.  Soil solution consists of water and dissolved minerals in the pores between soil particles  After a heavy rainfall, water drains from the larger spaces in the soil, but smaller spaces retain water because of its attraction to clay and other particles  Loams are the most fertile topsoils and contain equal amounts of sand, silt, and clay © 2014 Pearson Education, Inc.
  64. 64. Topsoil Composition  A soil's composition refers to its inorganic (mineral) and organic chemical components © 2014 Pearson Education, Inc.
  65. 65.  Inorganic components of the soil include positively charged ions (cations) and negatively charged ions (anions)  Most soil particles are negatively charged  Anions (for example, NO3 – , H2PO4 – , SO4 2– ) do not bind with negatively charged soil particles and can be lost from the soil by leaching © 2014 Pearson Education, Inc.
  66. 66.  Cations (for example, K+ , Ca2+ , Mg2+ ) adhere to negatively charged soil particles; this prevents them from leaching out of the soil through percolating groundwater  During cation exchange, cations are displaced from soil particles by other cations  Displaced cations enter the soil solution and can be taken up by plant roots © 2014 Pearson Education, Inc. Animation: Minerals from Soil
  67. 67. © 2014 Pearson Education, Inc. Figure 29.10 Soil particle K+ Root hair Cell wall Mg2+ K+ H+ H+ K+ Ca2+ Ca2+ H2O + CO2 H2CO3 HCO3 − +
  68. 68.  Organic components of the soil include decomposed leaves, feces, dead organisms, and other organic matter, which are collectively named humus  Humus forms a crumbly soil that retains water but is still porous  It also increases the soil's capacity to exchange cations and serves as a reservoir of mineral nutrients © 2014 Pearson Education, Inc.
  69. 69.  Living components of topsoil include bacteria, fungi, algae and other protists, insects, earthworms, nematodes, and plant roots  These organisms help to decompose organic material and mix the soil © 2014 Pearson Education, Inc.
  70. 70. Concept 29.4: Plant nutrition often involves relationships with other organisms  Plants and soil microbes have a mutualistic relationship  Dead plants provide energy needed by soil-dwelling microorganisms  Secretions from living roots support a wide variety of microbes in the near-root environment © 2014 Pearson Education, Inc.
  71. 71. Soil Bacteria and Plant Nutrition  Soil bacteria exchange chemicals with plant roots, enhance decomposition, and increase nutrient availability © 2014 Pearson Education, Inc.
  72. 72. Rhizobacteria  The soil layer surrounding the plant's roots is the rhizosphere  Rhizobacteria thrive in the rhizosphere, and some can enter roots  The rhizosphere has high microbial activity because of sugars, amino acids, and organic acids secreted by roots © 2014 Pearson Education, Inc.
  73. 73.  Rhizobacteria known as plant-growth-promoting rhizobacteria can play several roles  Produce hormones that stimulate plant growth  Produce antibiotics that protect roots from disease  Absorb toxic metals or make nutrients more available to roots © 2014 Pearson Education, Inc.
  74. 74. Bacteria in the Nitrogen Cycle  Nitrogen can be an important limiting nutrient for plant growth  The nitrogen cycle transforms atmospheric nitrogen and nitrogen-containing compounds  Plants can only absorb nitrogen as either NO3 – or NH4 +  Most usable soil nitrogen comes from actions of soil bacteria © 2014 Pearson Education, Inc.
  75. 75. © 2014 Pearson Education, Inc. Figure 29.11 ATMOSPHERE ATMOSPHERE SOIL SOIL Nitrogen-fixing bacteria N2 N2N2 NH3 (ammonia) H+ (from soil) Ammonifying bacteria Amino acids NH4 + (ammonium) NO2 − (nitrite)Nitrifying bacteria NO3 − (nitrate)Nitrifying bacteria Denitrifying bacteria Microbial decomposition Nitrate and nitrogenous organic compounds exported in xylem to shoot system NH4 + Root Proteins from humus (dead organic material)
  76. 76. © 2014 Pearson Education, Inc. Figure 29.11a ATMOSPHERE SOIL Nitrogen-fixing bacteria N2N2 NH3 (ammonia) H+ (from soil) Ammonifying bacteria Amino acids NH4 + (ammonium) NO2 − (nitrite)Nitrifying bacteria NO3 − (nitrate)Nitrifying bacteria Denitrifying bacteria Microbial decomposition Nitrate and nitrogenous organic compounds exported in xylem to shoot system NH4 + Root Proteins from humus (dead organic material)
  77. 77. © 2014 Pearson Education, Inc. Figure 29.11b ATMOSPHERE SOIL Nitrogen-fixing bacteria N2 NH3 (ammonia) H+ (from soil) Ammonifying bacteria Amino acids NH4 + (ammonium) NO2 − (nitrite)Nitrifying bacteria Microbial decomposition Proteins from humus (dead organic material)
  78. 78. © 2014 Pearson Education, Inc. Figure 29.11c N2 NO2 − (nitrite) NO3 − (nitrate)Nitrifying bacteria Denitrifying bacteria Nitrate and nitrogenous organic compounds exported in xylem to shoot system NH4 + Root
  79. 79.  Conversion to NH4 +  Ammonifying bacteria break down organic compounds and release ammonium (NH4 + )  Nitrogen-fixing bacteria convert N2 gas into NH3  NH3 is converted to NH4 +  Conversion to NO3 –  Nitrifying bacteria oxidize NH4 + to nitrite (NO2 – ) then nitrite to nitrate (NO3 – )  Different nitrifying bacteria mediate each step © 2014 Pearson Education, Inc.
  80. 80.  Nitrogen is lost to the atmosphere when denitrifying bacteria convert NO3 – to N2 © 2014 Pearson Education, Inc.
  81. 81. Nitrogen-Fixing Bacteria: A Closer Look  Nitrogen is abundant in the atmosphere but unavailable to plants due to the triple bond between atoms in N2  Nitrogen fixation is the conversion of nitrogen from N2 to NH3:  Some nitrogen-fixing bacteria are free-living; others form intimate associations with plant roots © 2014 Pearson Education, Inc. N2 + 8 e– + 8 H+ + 16 ATP → 2 NH3 + H2 + 16 ADP + 16
  82. 82.  Symbiotic relationships with nitrogen-fixing Rhizobium bacteria provide some legumes with a source of fixed nitrogen  Along a legume's roots are swellings called nodules, composed of plant cells "infected" by nitrogen-fixing Rhizobium bacteria © 2014 Pearson Education, Inc.
  83. 83. © 2014 Pearson Education, Inc. Figure 29.12 Roots Nodules
  84. 84.  Inside the root nodule, Rhizobium bacteria assume a form called bacteroids, which are contained within vesicles formed by the root cell  The plant obtains fixed nitrogen from Rhizobium, and Rhizobium obtains sugar and an anaerobic environment  Each legume species is associated with a particular strain of Rhizobium © 2014 Pearson Education, Inc.
  85. 85. Fungi and Plant Nutrition  Mycorrhizae are mutualistic associations of fungi and roots  The fungus benefits from a steady supply of sugar from the host plant  The host plant benefits because the fungus increases the surface area for water uptake and mineral absorption  Mycorrhizal fungi also secrete growth factors that stimulate root growth and branching © 2014 Pearson Education, Inc.
  86. 86. The Two Main Types of Mycorrhizae  Mycorrhizal associations consist of two major types  Ectomycorrhizae  Arbuscular mycorrhizae © 2014 Pearson Education, Inc.
  87. 87. © 2014 Pearson Education, Inc. Figure 29.13 Epidermis Cortex Epidermal cell Endodermis Mantle (fungal sheath) Mantle (fungal sheath) Fungal hyphae between cortical cells (LM) 50 µm 1.5 mm (ColorizedSEM) Epidermis Cortex Fungal vesicle Endodermis Cortical cell Casparian strip Plasma membrane Arbuscules (LM) 10µm Root hair Fungal hyphae (a) Ectomycorrhizae (b) Arbuscular mycorrhizae (endomycorrhizae)
  88. 88. © 2014 Pearson Education, Inc. Figure 29.13a Epidermis Cortex Epidermal cell Endodermis Mantle (fungal sheath) Mantle (fungal sheath) Fungal hyphae between cortical cells (LM) 50 µm 1.5 mm (ColorizedSEM) (a) Ectomycorrhizae
  89. 89. © 2014 Pearson Education, Inc. Figure 29.13aa Mantle (fungal sheath) 1.5 mm (ColorizedSEM)
  90. 90. © 2014 Pearson Education, Inc. Figure 29.13ab Epidermal cell (LM) 50 µm Fungal hyphae between cortical cells
  91. 91. © 2014 Pearson Education, Inc. Figure 29.13b Epidermis Cortex Fungal vesicle Endodermis Cortical cell Casparian strip Plasma membrane Arbuscules (LM) 10µm Root hair Fungal hyphae (b) Arbuscular mycorrhizae (endomycorrhizae)
  92. 92. © 2014 Pearson Education, Inc. Figure 29.13ba Cortical cell Arbuscules (LM) 10µm
  93. 93.  In ectomycorrhizae, the mycelium of the fungus forms a dense sheath over the surface of the root  These hyphae form a network in the apoplast but do not penetrate the root cells  Ectomycorrhizae occur in about 10% of plant families, most of which are woody (for example, pine, birch, and eucalyptus) © 2014 Pearson Education, Inc.
  94. 94.  In arbuscular mycorrhizae, microscopic fungal hyphae extend into the root  These mycorrhizae penetrate the cell wall but not the plasma membrane to form branched arbuscules within root cells  The arbuscules are important sites of nutrient transfer  Arbuscular mycorrhizae occur in about 85% of plant species, including most crops © 2014 Pearson Education, Inc.
  95. 95. Agricultural and Ecological Importance of Mycorrhizae  Seeds can be inoculated with fungal spores to promote formation of mycorrhizae  Some invasive exotic plants disrupt interactions between native plants and their mycorrhizal fungi  For example, garlic mustard slows growth of other plants by preventing the growth of mycorrhizal fungi © 2014 Pearson Education, Inc.
  96. 96. © 2014 Pearson Education, Inc. Figure 29.14 Experiment Results Invaded Uninvaded Sterilized invaded Sterilized uninvaded Soil type Invaded Uninvaded Soil type White ash Sugar maple Seedlings Red maple Mycorrhizal colonization(%) Increasein plantbiomass(%) 300 200 100 0 30 20 10 0 40
  97. 97. © 2014 Pearson Education, Inc. Figure 29.14a Experiment
  98. 98. © 2014 Pearson Education, Inc. Figure 29.14b Results Invaded Uninvaded Sterilized invaded Sterilized uninvaded Soil type Invaded Uninvaded Soil type White ash Sugar maple Seedlings Red maple Mycorrhizal colonization(%) Increasein plantbiomass(%) 300 200 100 0 30 20 10 0 40
  99. 99. 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 © 2014 Pearson Education, Inc. Video: Sundew Traps Prey
  100. 100.  Epiphytes grow on other plants and obtain water and minerals from rain, rather than tapping their hosts for sustenance © 2014 Pearson Education, Inc.
  101. 101. © 2014 Pearson Education, Inc. Figure 29.15a Staghorn fern, an epiphyte
  102. 102.  Parasitic plants absorb water, sugars, and minerals from their living host plant  Some species also photosynthesize, but others rely entirely on the host plant for sustenance  Some species parasitize the mycorrhizal hyphae of other plants © 2014 Pearson Education, Inc.
  103. 103. © 2014 Pearson Education, Inc. Figure 29.15b Parasitic plants Mistletoe, a photosynthetic parasite Dodder, a nonphoto- synthetic parasite (orange) Indian pipe, a nonphoto- synthetic parasite of mycorrhizae
  104. 104. © 2014 Pearson Education, Inc. Figure 29.15ba Mistletoe, a photosynthetic parasite
  105. 105. © 2014 Pearson Education, Inc. Figure 29.15bb Dodder, a nonphoto- synthetic parasite (orange)
  106. 106. © 2014 Pearson Education, Inc. Figure 29.15bc Indian pipe, a nonphoto- synthetic parasite of mycorrhizae
  107. 107.  Carnivorous plants are photosynthetic but obtain nitrogen by killing and digesting mostly insects © 2014 Pearson Education, Inc.
  108. 108. © 2014 Pearson Education, Inc. Figure 29.15c Carnivorous plants Pitcher plants Venus flytraps Sundew
  109. 109. © 2014 Pearson Education, Inc. Figure 29.15ca Pitcher plants
  110. 110. © 2014 Pearson Education, Inc. Figure 29.15cb Pitcher plants
  111. 111. © 2014 Pearson Education, Inc. Figure 29.15cc Sundew
  112. 112. © 2014 Pearson Education, Inc. Figure 29.15cd Venus flytrap
  113. 113. © 2014 Pearson Education, Inc. Figure 29.15ce Venus flytrap
  114. 114. 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 © 2014 Pearson Education, Inc.
  115. 115. Absorption of Water and Minerals by Root Cells  Most water and mineral absorption occurs near root tips, where root hairs are located and the epidermis is permeable to water  Root hairs account for much of the absorption of water by roots  After soil solution enters the roots, the extensive surface area of cortical cell membranes enhances uptake of water and selected minerals © 2014 Pearson Education, Inc.
  116. 116.  The concentration of essential minerals is greater in the roots than in the soil because of active transport © 2014 Pearson Education, Inc.
  117. 117.  The endodermis is the innermost layer of cells in the root cortex  It surrounds the vascular cylinder and is the last checkpoint for selective passage of minerals from the cortex into the vascular tissue  Water can cross the cortex via the symplast or apoplast Transport of Water and Minerals into the Xylem © 2014 Pearson Education, Inc. Animation: Transport in Roots
  118. 118. © 2014 Pearson Education, Inc. Figure 29.16 Apoplastic route Symplastic route Transmembrane route The endodermis: controlled entry to the vascular cylinder (stele) Apoplastic route Symplastic route Root hair Plasma membrane Epidermis Casparian strip Vascular cylinder (stele) Vessels (xylem) Cortex Endodermis Pathway along apoplast Transport in the xylem Casparian strip Pathway through symplast Endodermal cell 1 1 2 2 4 5 3 3 4 5 5 4
  119. 119. © 2014 Pearson Education, Inc. Figure 29.16a Apoplastic route Symplastic route Transmembrane route The endodermis: controlled entry to the vascular cylinder (stele) Apoplastic route Symplastic route Root hair Plasma membrane Epidermis Casparian strip Vascular cylinder (stele) Vessels (xylem) Cortex Endodermis Transport in the xylem 1 1 2 2 3 4 3 4 5 5
  120. 120. © 2014 Pearson Education, Inc. Figure 29.16b The endodermis: controlled entry to the vascular cylinder (stele) Pathway along apoplast Transport in the xylem Casparian strip Pathway through symplast Endodermal cell 5 4 5 4
  121. 121.  Water and minerals can travel to the vascular cylinder through the cortex via  The apoplastic route, along cell walls and extracellular spaces  The symplastic route, in the cytoplasm, moving between cells through plasmodesmata  The transmembrane route, moving from cell to cell by crossing cell membranes and cell walls © 2014 Pearson Education, Inc.
  122. 122.  The waxy Casparian strip of the endodermal wall blocks apoplastic transfer of minerals from the cortex to the vascular cylinder  Water and minerals in the apoplast must cross the plasma membrane of an endodermal cell to enter the vascular cylinder © 2014 Pearson Education, Inc.
  123. 123.  The endodermis regulates and transports needed minerals from the soil into the xylem  Water and minerals move from the protoplasts of endodermal cells into their cell walls  Diffusion and active transport are involved in this movement from symplast to apoplast  Water and minerals now enter the tracheids and vessel elements © 2014 Pearson Education, Inc.
  124. 124. Bulk Flow Transport via the Xylem  Xylem sap, water and dissolved minerals, is transported from roots to leaves by bulk flow  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 © 2014 Pearson Education, Inc.
  125. 125. 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 © 2014 Pearson Education, Inc.
  126. 126.  Transpirational pull is generated when water vapor in the air spaces of a leaf diffuses down its water potential gradient and exits the leaf via stomata  As water evaporates, the air-water interface retreats farther into the mesophyll cell walls and becomes more curved  Due to the high surface tension of water, the curvature of the interface creates a negative pressure potential © 2014 Pearson Education, Inc.
  127. 127.  This negative pressure pulls water in the xylem into the leaf  The pulling effect results from the cohesive binding between water molecules  The transpirational pull on xylem sap is transmitted from leaves to roots © 2014 Pearson Education, Inc. Animation: Transpiration Animation: Water Transport in Plants Animation: Water Transport
  128. 128. © 2014 Pearson Education, Inc. Figure 29.17 Xylem Microfibrils in cell wall of mesophyll cell Microfibril (cross section) Air-water interface Water film Cuticle Mesophyll Cuticle Stoma Air space Upper epidermis Lower epidermis
  129. 129. © 2014 Pearson Education, Inc. Figure 29.17a Xylem Microfibrils in cell wall of mesophyll cell Cuticle Mesophyll Cuticle Stoma Air space Upper epidermis Lower epidermis
  130. 130. © 2014 Pearson Education, Inc. Figure 29.17b Microfibrils in cell wall of mesophyll cell Microfibril (cross section) Air-water interface Water film
  131. 131. © 2014 Pearson Education, Inc. Figure 29.18 Cohesion by hydrogen bonding Water molecule Cohesion and adhesion in the xylem Water uptake from soil Water Soil particle Root hair Cell wall Transpiration Xylem cells Water molecule Adhesion by hydrogen bonding Xylem sap Mesophyll cells Stoma Atmosphere Outside air ψ Waterpotentialgradient Leaf ψ (air spaces) Trunk xylem ψ Leaf ψ (cell walls) Trunk xylem ψ Soil ψ −7.0 MPa −100.0 MPa= = −1.0 MPa= −0.8 MPa= −0.6 MPa= −0.3 MPa=
  132. 132. © 2014 Pearson Education, Inc. Figure 29.18a Water molecule Water uptake from soil Water Soil particle Root hair
  133. 133. © 2014 Pearson Education, Inc. Figure 29.18b Cohesion by hydrogen bonding Cohesion and adhesion in the xylem Cell wall Xylem cells Adhesion by hydrogen bonding
  134. 134. © 2014 Pearson Education, Inc. Figure 29.18c Transpiration Water molecule Xylem sap Mesophyll cells Stoma Atmosphere
  135. 135.  Cohesion and adhesion in the ascent of xylem sap: Water molecules are attracted to each other through cohesion  Cohesion makes it possible to pull a column of xylem sap  Water molecules are attracted to hydrophilic walls of xylem cell walls through adhesion  Adhesion of water molecules to xylem cell walls helps offset the force of gravity © 2014 Pearson Education, Inc.
  136. 136.  Thick secondary walls prevent vessel elements and tracheids from collapsing under negative pressure  Drought stress or freezing can cause cavitation, the formation of a water vapor pocket by a break in the chain of water molecules © 2014 Pearson Education, Inc.
  137. 137. Xylem Sap Ascent by Bulk Flow: A Review  Bulk flow is driven by a water potential difference at opposite ends of xylem tissue  Bulk flow is driven by evaporation and does not require energy from the plant; like photosynthesis, it is solar powered © 2014 Pearson Education, Inc.
  138. 138.  Bulk flow differs from diffusion  It is driven by differences in pressure potential, not solute potential  It occurs in hollow dead cells, not across the membranes of living cells  It moves the entire solution, not just water or solutes  It is much faster © 2014 Pearson Education, Inc.
  139. 139. Concept 29.6: The rate of transpiration is regulated by stomata  Leaves generally have broad surface areas and high surface-to-volume ratios  These characteristics increase photosynthesis and increase water loss through stomata  Guard cells help balance water conservation with gas exchange for photosynthesis © 2014 Pearson Education, Inc.
  140. 140. Stomata: Major Pathways for Water Loss  About 95% of the water a plant loses escapes through stomata  Each stoma is flanked by a pair of guard cells, which control the diameter of the stoma by changing shape  Stomatal density is under genetic and environmental control © 2014 Pearson Education, Inc.
  141. 141. Mechanisms of Stomatal Opening and Closing  Changes in turgor pressure open and close stomata  When turgid, guard cells bow outward and the pore between them opens  When flaccid, guard cells become less bowed and the pore closes © 2014 Pearson Education, Inc.
  142. 142. © 2014 Pearson Education, Inc. Figure 29.19 Guard cells turgid/Stoma open K+ Guard cells flaccid/Stoma closed H2O Radially oriented cellulose microfibrils Cell wall Vacuole (a) Changes in guard cell shape and stomatal opening and closing (surface view) Guard cell (b) Role of potassium ions (K+ ) in stomatal opening and closing H2O H2O H2O H2O H2O H2O H2O H2OH2O
  143. 143. © 2014 Pearson Education, Inc. Figure 29.19a Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed Radially oriented cellulose microfibrils Cell wall Vacuole (a) Changes in guard cell shape and stomatal opening and closing (surface view) Guard cell
  144. 144. © 2014 Pearson Education, Inc. Figure 29.19b K+ H2O (b) Role of potassium ions (K+ ) in stomatal opening and closing H2O H2O H2O H2O H2O H2O H2O H2OH2O Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed
  145. 145.  Changes in turgor pressure result primarily from the reversible uptake and loss of potassium ions (K+ ) by the guard cells © 2014 Pearson Education, Inc.
  146. 146. Stimuli for Stomatal Opening and Closing  Generally, stomata open during the day and close at night to minimize water loss  Stomatal opening at dawn is triggered by  Light  CO2 depletion  An internal "clock" in guard cells  All eukaryotic organisms have internal clocks; circadian rhythms are 24-hour cycles © 2014 Pearson Education, Inc.
  147. 147.  Drought stress can cause stomata to close during the daytime  The hormone abscisic acid (ABA) is produced in response to water deficiency and causes the closure of stomata © 2014 Pearson Education, Inc.
  148. 148. Effects of Transpiration on Wilting and Leaf Temperature  Plants lose a large amount of water by transpiration  If the lost water is not replaced by sufficient transport of water, the plant will lose water and wilt  Transpiration also results in evaporative cooling, which can lower the temperature of a leaf and prevent protein denaturation © 2014 Pearson Education, Inc.
  149. 149. Adaptations That Reduce Evaporative Water Loss  Xerophytes are plants adapted to arid climates © 2014 Pearson Education, Inc.
  150. 150. © 2014 Pearson Education, Inc. Figure 29.20 Old man cactus (Cephalocereus senilis) Ocotillo (Fouquieria splendens) Oleander (Nerium oleander) Thick cuticle Upper epidermal tissue Stoma Lower epidermal tissue CryptTrichomes ("hairs") 100µm
  151. 151. © 2014 Pearson Education, Inc. Figure 29.20a Ocotillo (leafless)
  152. 152. © 2014 Pearson Education, Inc. Figure 29.20b Ocotillo after heavy rain
  153. 153. © 2014 Pearson Education, Inc. Figure 29.20c Ocotillo leaves
  154. 154. © 2014 Pearson Education, Inc. Figure 29.20d Oleander leaf cross section Thick cuticle Upper epidermal tissue Stoma Lower epidermal tissue CryptTrichomes ("hairs") 100µm
  155. 155. © 2014 Pearson Education, Inc. Figure 29.20e Oleander flowers
  156. 156. © 2014 Pearson Education, Inc. Figure 29.20f Old man cactus
  157. 157.  Some desert plants complete their life cycle during the rainy season  Others have leaf modifications that reduce the rate of transpiration  Some plants use a specialized form of photosynthesis called crassulacean acid metabolism (CAM) where stomatal gas exchange occurs at night © 2014 Pearson Education, Inc.
  158. 158. Concept 29.7: Sugars are transported from sources to sinks via the phloem  The products of photosynthesis are transported through phloem by the process of translocation © 2014 Pearson Education, Inc.
  159. 159. Movement from Sugar Sources to Sugar Sinks  In angiosperms, sieve-tube elements are the conduits for translocation  Phloem sap is an aqueous solution that is high in sucrose  It travels from a sugar source to a sugar sink  A sugar source is an organ that is a net producer of sugar, such as mature leaves  A sugar sink is an organ that is a net consumer or storer of sugar, such as a tuber or bulb © 2014 Pearson Education, Inc.
  160. 160.  A storage organ can be both a sugar sink in summer and sugar source in winter  Sugar must be loaded into sieve-tube elements before being exported to sinks  Depending on the species, sugar may move by symplastic or both symplastic and apoplastic pathways  Companion cells enhance solute movement between the apoplast and symplast © 2014 Pearson Education, Inc.
  161. 161. © 2014 Pearson Education, Inc. Figure 29.21 Apoplast Symplast Cell walls (apoplast) Plasmodesmata Mesophyll cell Plasma membrane Companion (transfer) cell Sieve-tube element Mesophyll cell Bundle- sheath cell Phloem parenchyma cell (a) Sucrose manufactured in mesophyll cells can travel via the symplast (blue arrows) to sieve-tube elements. (b) A chemiosmotic mechanism is responsible for the active transport of sucrose. High H+ concentration Low H+ concentration Proton pump Cotransporter Sucrose S S H+ H+ H+
  162. 162. © 2014 Pearson Education, Inc. Figure 29.21a Apoplast Symplast Cell walls (apoplast) Plasmodesmata Mesophyll cell Plasma membrane Companion (transfer) cell Sieve-tube element Mesophyll cell Bundle- sheath cell Phloem parenchyma cell (a) Sucrose manufactured in mesophyll cells can travel via the symplast (blue arrows) to sieve-tube elements.
  163. 163. © 2014 Pearson Education, Inc. Figure 29.21b (b) A chemiosmotic mechanism is responsible for the active transport of sucrose. High H+ concentration Low H+ concentration Proton pump Cotransporter Sucrose S S H+ H+ H+
  164. 164.  In most plants, phloem loading requires active transport  Proton pumping and cotransport of sucrose and H+ enable the cells to accumulate sucrose  At the sink, sugar molecules diffuse from the phloem to sink tissues and are followed by water © 2014 Pearson Education, Inc.
  165. 165. Bulk Flow by Positive Pressure: The Mechanism of Translocation in Angiosperms  Phloem sap moves through a sieve tube by bulk flow driven by positive pressure called pressure flow © 2014 Pearson Education, Inc. Animation: Phloem Translocation Spring Animation: Phloem Translocation Summer
  166. 166. © 2014 Pearson Education, Inc. Figure 29.22 Loading of sugar H2O Vessel (xylem) Source cell (leaf) Sieve tube (phloem) H2O Sucrose Uptake of water Unloading of sugar Recycling of water Sink cell (storage root) H2O Sucrose Bulkflowbynegativepressure Bulkflowbypositivepressure 1 1 2 2 3 4 3 4
  167. 167.  Sometimes there are more sinks than can be supported by sources  Self-thinning is the dropping of sugar sinks such as flowers, seeds, or fruits © 2014 Pearson Education, Inc.
  168. 168. © 2014 Pearson Education, Inc. Figure 29.UN01a
  169. 169. © 2014 Pearson Education, Inc. Figure 29.UN01b
  170. 170. © 2014 Pearson Education, Inc. Figure 29.UN02 Minerals H2O O2 CO2 H2O O2 CO2
  171. 171. © 2014 Pearson Education, Inc. Figure 29.UN03

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Biology in Focus - Resource Acquisition, Nutrition and Transport in Vascular Plants

Campbell Biology 9th Edition Lecture Slides Chapter 29

Source: https://www.slideshare.net/mpattani/biology-in-focus-chapter-29