CO O2 2 Light

Sugar H2O

O2

H2O and CO2 minerals

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Cell wall 24 32 42 29 40 16 Apoplastic route 11 19 21 27 34 8 3 6 Cytosol 14 13 Symplastic route 26 Shoot 1 5 apical 22 Transmembrane route meristem 9 Buds 18 10 4 31 2 17 23 7 12 Key 15 Plasmodesma 20 25 28 Plasma membrane Apoplast 1 mm Symplast

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CYTOPLASM EXTRACELLULAR + S H+ H FLUID H+ + H+ H + Hydrogen + H ion H H+ + S S H + H + Initial flaccid cell: + + H H H + ψP = 0 H+ H ψS = −0.7 H+ + S S S 0.4 M sucrose Proton H H+ ψ = −0.7 MPa Pure water: + solution: pump H ψP = 0 + ψP = 0 H /sucrose Sucrose Plasmolyzed ψS = 0 Turgid cell ψ = −0.9 (a) H+ and membrane potential cotransporter (neutral solute) cell at osmotic S ψ = 0 MPa at osmotic equilibrium ψ = −0.9 MPa equilibrium (b) H+ and cotransport of neutral solutes with its with its + H+ − H surroundings surroundings 3 NO − ψP = 0 ψP = 0.7 + 3 H NO + ψS = −0.9 ψS = −0.7 + H+ K Potassium ion H ψ = −0.9 MPa ψ = 0 MPa + + H Nitrate K H+ K+ + − H+ K NO3 (a) Initial conditions: (b) Initial conditions: − + 3 NO − K cellular ψ > environmental ψ cellular ψ < environmental ψ 3 − NO + + NO3 K K H+ + − + H /NO3 + H cotransporter H Ion channel (c) H+ and cotransport of ions (d) Ion channels

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Wilted

Turgid

Control: Solution Experimental: Solution containing all minerals without potassium

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Healthy

Phosphate-deficient

Potassium-deficient

Nitrogen-deficient

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ATMOSPHERE

Soil particle N + 2 K K+

2+ SOIL 2+ 2+ Ca Ca K+ Mg H+ N2 ATMOSPHERE N2 − + Nitrate and H2O + CO2 H2CO3 HCO3 + H SOIL Proteins from humus nitrogenous (dead organic material) organic compounds Nitrogen-fixing Microbial bacteria exported in decomposition xylem to Amino acids Denitrifying shoot system Root hair NH3 (ammonia) Ammonifying bacteria bacteria NH + H+ 4 (from soil) + − − Cell wall NH4 NO2 NO3 (ammonium) Nitrifying (nitrite) Nitrifying (nitrate) bacteria bacteria

Root

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Epidermal cell

Endodermis

Fungal

(Colorized SEM) (Colorized hyphae between 1.5 mm cortical Nodules Mantle cells (LM) (fungal sheath) 50 µm (a) Ectomycorrhizae

Epidermis Cortex Cortical cell

Endodermis Fungal Fungal hyphae vesicle Roots Casparian strip m µ Root Arbuscules hair 10 Plasma membrane (LM) (b) Arbuscular mycorrhizae (endomycorrhizae) © 2014 Pearson Education, Inc. 13 © 2014 Pearson Education, Inc. 14

Experiment Results 300

200

100

Increase in 0

plant biomass(%) plant Invaded Uninvaded Sterilized Sterilized invaded uninvaded Soil type

40 30

20 Seedlings 10

Mycorrhizal Sugar maple

colonization (%) colonization 0 Red maple Invaded Uninvaded White ash Soil type

Staghorn fern, an epiphyte © 2014 Pearson Education, Inc. 15 © 2014 Pearson Education, Inc. 16

Carnivorous plants Parasitic plants

Sundew Pitcher plants

Venus flytraps

Mistletoe, a photosynthetic Dodder, a nonphoto- Indian pipe, a nonphoto- parasite synthetic parasite synthetic parasite of (orange) mycorrhizae

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4 Pathway 5 Cuticle Xylem through Upper symplast epidermis 1 Apoplastic route Casparian strip Plasma Microfibrils in membrane cell wall of Mesophyll Apoplastic mesophyll cell 1 Air route space 2 Symplastic 3 route 2 4 5 Vessels (xylem) Lower Symplastic Root epidermis route hair Cuticle Stoma 3 Transmembrane route Epidermis Microfibril Endodermis Vascular Water Air-water (cross section) cylinder film interface 4 The endodermis: controlled entry Cortex (stele) to the vascular cylinder (stele) 5 Transport in the xylem

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Xylem sap Guard cells turgid/Stoma open Guard cells flaccid/Stoma closed Radially oriented Outside air ψ Mesophyll cells cellulose microfibrils = −100.0 MPa Stoma Cell Leaf ψ (air spaces) Water molecule wall = −7.0 MPa Transpiration Atmosphere Leaf ψ (cell walls) Adhesion by hydrogen = −1.0 MPa Xylem bonding cells Cell wall Vacuole Guard cell (a) Changes in guard cell shape and stomatal opening and closing (surface view)

Trunk xylem ψ Cohesion H O H2O 2 H2O = −0.8 MPa Cohesion by hydrogen H2O and adhesion bonding + H O Water potential gradient gradient potential Water in the xylem K 2 H2O Water molecule

Trunk xylem Root hair ψ H2O = −0.6 MPa Soil particle H O H O 2 2 H2O Water Soil ψ Water uptake from soil = −0.3 MPa (b) Role of potassium ions (K+) in stomatal opening and closing © 2014 Pearson Education, Inc. 21 © 2014 Pearson Education, Inc. 22

Ocotillo Oleander (Nerium oleander) (Fouquieria Thick cuticle Upper epidermal tissue splendens)

Apoplast Symplast

Companion Mesophyll cell (transfer) cell High H+ concentration + Cotransporter m Cell walls (apoplast) Sieve-tube Proton H µ Plasma element pump S membrane 100 Trichomes Crypt Stoma Lower epidermal Plasmodesmata (“hairs”) tissue

H+ H+ Sucrose Bundle- Phloem S Mesophyll Low H+ concentration cell sheath cell parenchyma cell (a) Sucrose manufactured in mesophyll cells (b) A chemiosmotic mechanism is can travel via the symplast (blue arrows) responsible for the active transport of to sieve-tube elements. sucrose.

Old man cactus (Cephalocereus senilis) © 2014 Pearson Education, Inc. 23 © 2014 Pearson Education, Inc. 24 Sieve Source cell Vessel tube (leaf) (xylem) (phloem) 1 Loading of sugar

H2O 1 Sucrose

H2O 2

2 Uptake of water

3 Unloading of sugar Sink cell (storage root) Bulk flow by negativepressureby flow Bulk Bulk flow by positive pressure positive by flow Bulk 4 Recycling of water 4 3 Sucrose H2O

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