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Figure 29.1 Plants or pebbles?
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O2 CO2 Light Sugar H2O O2 H2O and minerals CO2
Figure An overview of resource acquisition and transport in a vascular plant (step 3) O2 H2O and minerals CO2 2
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24 32 42 29 40 16 11 19 21 27 8 3 34 6 14 13 26 Shoot apical meristem 1 22 5 9 18 Buds 10 4 2 31 17 Figure 29.3 Emerging phyllotaxy of Norway spruce 23 7 12 15 20 25 28 1 mm
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Cell wall Apoplastic route Cytosol Symplastic route
Transmembrane route Key Figure 29.4 Cell compartments and routes for short-distance transport Plasmodesma Apoplast Plasma membrane Symplast 4
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(a) H+ and membrane potential
CYTOPLASM EXTRACELLULAR FLUID H+ S H+ H+ H+ H+ Hydrogen ion H+ H+ S H+ S H+ H+ H+ H+ H+ H+ H+ S H+ S H+ S Proton pump H+ H+ H+/sucrose cotransporter Sucrose (neutral solute) (a) H+ and membrane potential (b) H+ and cotransport of neutral solutes H+ H+ NO3− NO3− H+ H+ K+ Potassium ion H+ H+ K+ Nitrate H+ K+ Figure 29.5 Solute transport across plant cell plasma membranes K+ H+ NO3− NO3− NO3− K+ NO3− K+ K+ H+ H+/NO3− cotransporter H+ H+ Ion channel (c) H+ and cotransport of ions (d) Ion channels 5
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(a) Initial conditions: cellular environmental
Initial flaccid cell: P S −0.7 0.4 M sucrose solution: −0.7 MPa Pure water: P S Plasmolyzed cell at osmotic equilibrium with its surroundings −0.9 P S Turgid cell at osmotic equilibrium with its surroundings 0 MPa −0.9 MPa −0.9 P S 0.7 P S −0.7 −0.9 MPa 0 MPa Figure 29.6 Water relations in plant cells (a) Initial conditions: cellular environmental (b) Initial conditions: cellular environmental 6
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Wilted Turgid Figure 29.7 A moderately wilted plant can regain its turgor when watered. 7
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containing all minerals Experimental: Solution without potassium
Technique Figure 29.8 Research method: hydroponic culture Control: Solution containing all minerals Experimental: Solution without potassium 8
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Table 29.1 Essential elements in plants
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Healthy Phosphate-deficient Potassium-deficient Nitrogen-deficient
Figure 29.9 The most common mineral deficiencies, as seen in maize leaves Nitrogen-deficient 10
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Soil particle Root hair Cell wall K+ K+ Ca2+ Ca2+ Mg2+ K+ H+ H2O + CO2
H2CO3 HCO3− + H+ Figure Cation exchange in soil Root hair Cell wall 11
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(dead organic material)
ATMOSPHERE N2 SOIL N2 ATMOSPHERE N2 Nitrate and nitrogenous organic compounds exported in xylem to shoot system SOIL Proteins from humus (dead organic material) Nitrogen-fixing bacteria Microbial decomposition Figure The roles of soil bacteria in the nitrogen nutrition of plants Amino acids NH3 (ammonia) Denitrifying bacteria Ammonifying bacteria NH4+ H+ (from soil) NH4+ (ammonium) NO2− (nitrite) NO3− (nitrate) Nitrifying bacteria Nitrifying bacteria Root 12
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Nodules Figure Soybean root nodules Roots 13
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Mantle (fungal sheath)
Epidermis Cortex Mantle (fungal sheath) Epidermal cell (Colorized SEM) Endodermis Fungal hyphae between cortical cells 1.5 mm Mantle (fungal sheath) (LM) 50 m (a) Ectomycorrhizae Epidermis Cortex Cortical cell Figure Mycorrhizae Endodermis Fungal hyphae Fungal vesicle Casparian strip Root hair 10 m Arbuscules Plasma membrane (LM) (b) Arbuscular mycorrhizae (endomycorrhizae) 14
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Experiment Results 300 200 plant biomass (%) Increase in 100 Invaded
Invaded Uninvaded Sterilized invaded Sterilized uninvaded Soil type 40 30 colonization (%) Mycorrhizal Figure Inquiry: Does the invasive weed garlic mustard disrupt mutualistic associations between native tree seedlings and arbuscular mycorrhizal fungi? 20 Seedlings 10 Sugar maple Red maple Invaded Uninvaded White ash Soil type 15
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Staghorn fern, an epiphyte
Figure 29.15a Exploring unusual nutritional adaptations in plants (part 1: epiphytes) Staghorn fern, an epiphyte 16
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Mistletoe, a photosynthetic parasite Dodder, a nonphoto-
Parasitic plants Figure 29.15b Exploring unusual nutritional adaptations in plants (part 2: parasitic plants) Mistletoe, a photosynthetic parasite Dodder, a nonphoto- synthetic parasite (orange) Indian pipe, a nonphoto- synthetic parasite of mycorrhizae 17
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Carnivorous plants Sundew Pitcher plants Venus flytraps
Figure 29.15c Exploring unusual nutritional adaptations in plants (part 3: carnivorous plants) 18
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The endodermis: controlled entry to the vascular cylinder (stele) 5
Casparian strip Endodermal cell Pathway along apoplast 4 Pathway through symplast 5 1 Apoplastic route Casparian strip Plasma membrane Apoplastic route 1 2 Symplastic route 3 Figure Transport of water and minerals from root hairs to the xylem 2 4 5 Vessels (xylem) Symplastic route Root hair 3 Transmembrane route Epidermis Endodermis Vascular cylinder (stele) Cortex 4 The endodermis: controlled entry to the vascular cylinder (stele) 5 Transport in the xylem 19
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Cuticle Xylem Upper epidermis Microfibrils in cell wall of
mesophyll cell Mesophyll Air space Figure Generation of transpirational pull Lower epidermis Cuticle Stoma Microfibril (cross section) Water film Air-water interface 20
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Outside air = −100.0 MPa Leaf (air spaces) = −7.0 MPa
Xylem sap Outside air Mesophyll cells = −100.0 MPa Stoma Leaf (air spaces) Water molecule = −7.0 MPa Atmosphere Transpiration Leaf (cell walls) Adhesion by hydrogen bonding = −1.0 MPa Xylem cells Cell wall Water potential gradient Trunk xylem Cohesion by hydrogen bonding −0.8 MPa Cohesion and adhesion in the xylem Figure Ascent of xylem sap Water molecule Trunk xylem Root hair −0.6 MPa Soil particle Water Soil Water uptake from soil −0.3 MPa 21
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Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed
Radially oriented cellulose microfibrils Cell wall Vacuole Guard cell (a) Changes in guard cell shape and stomatal opening and closing (surface view) H2O H2O H2O H2O Figure Mechanisms of stomatal opening and closing H2O K+ H2O H2O H2O H2O H2O (b) Role of potassium ions (K+) in stomatal opening and closing 22
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Oleander (Nerium oleander)
Ocotillo (Fouquieria splendens) Oleander (Nerium oleander) Thick cuticle Upper epidermal tissue 100 m Trichomes (“hairs”) Crypt Stoma Lower epidermal tissue Figure Some xerophytic adaptations Old man cactus (Cephalocereus senilis) 23
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(a) Sucrose manufactured in mesophyll cells
Apoplast Symplast Companion (transfer) cell Mesophyll cell High H+ concentration Cotransporter Cell walls (apoplast) H+ Sieve-tube element Proton pump Plasma membrane S Plasmodesmata Figure Loading of sucrose into phloem H+ H+ Sucrose Mesophyll cell Bundle- sheath cell Phloem parenchyma cell S Low H+ concentration (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. 24
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Sieve tube (phloem) Vessel (xylem)
Source cell (leaf) Vessel (xylem) 1 Loading of sugar H2O 1 Sucrose H2O 2 2 Uptake of water Bulk flow by negative pressure Bulk flow by positive pressure 3 Unloading of sugar Sink cell (storage root) Figure Bulk flow by positive pressure (pressure flow) in a sieve tube 4 Recycling of water 4 3 Sucrose H2O 25
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