2014 Pearson Education, Inc. 27 Cytosol Pearson Education, Inc. Plasmolyzed cell at osmotic equilibrium with its surroundings.

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1 CO O Light ugar O and minerals Apoplastic 7 Cytosol hoot apical meristem 8 8 Buds 9 CO ymplastic Trans Key Plasmodesma Apoplast ymplast mm CYTOPLAM EXTRACELLULAR FLUID ydrogen ion Proton pump /sucrose cotransporter (a) and potential Initial flaccid : 0. M sucrose solution: Plasmolyzed at osmotic equilibrium with its surroundings ucrose (neutral solute) (b) and cotransport of neutral solutes NO NO O NO N Nitrate /NO cotransporter NO (c) and cotransport of ions NO Potassium ion ψ 0.9 ψ 0.9 MPa ψ 0.7 ψ 0.7 MPa Pure water: ψ 0 ψ 0 MPa Turgid at osmotic equilibrium with its surroundings ψ ψ 0.7 ψ 0.9 MPa ψ (a) Initial conditions: ular ψ > environmental ψ 0 MPa (b) Initial conditions: ular ψ < environmental ψ Ion channel (d) Ion channels 6

2 Technique Wilted Turgid Control: olution containing all minerals Experimental: olution without potassium 7 8 ealthy Phosphate-deficient Potassium-deficient Nitrogen-deficient 9 0 ATMOPERE K oil particle K N Ca K Mg Ca OIL O CO CO CO hair N ATMOPERE OIL Nitrogen-fixing N (ammonia) (from soil) N (ammonium) Proteins from humus (dead organic material) Microbial decomposition Amino acids Ammonifying Nitrifying NO (nitrite) Denitrifying Nitrifying N NO (nitrate) Nitrate and nitrogenous organic compounds exported in xylem to shoot system N

3 (Colorized EM) Epidermal Endodermis hyphae between cortical s. mm Mantle (fungal sheath) Nodules Mantle (fungal sheath) (LM) 0 µm (a) Ectomycorrhizae Cortical Endodermis s hair (b) Arbuscular mycorrhizae (endomycorrhizae) (LM) Results Mycorrhizal colonization (%) Increase in plant biomass (%) Experiment 0 µm vesicle Casparian strip Arbuscules hyphae 0 Invaded Uninvaded terilized terilized invaded uninvaded oil type eedlings 0 0 Invaded Uninvaded oil type ugar maple Red maple White ash taghorn fern, an epiphyte 6 Carnivorous plants Parasitic plants undew Pitcher plants Venus flytraps Mistletoe, a photosynthetic parasite Dodder, a nonphoto- Indian pipe, a nonphotosynthetic parasite synthetic parasite of (orange) mycorrhizae 7 8

4 Casparian strip Endodermal Pathway along apoplast Pathway through symplast Apoplastic Upper epidermis Casparian strip ymplastic Mesophyll Apoplastic ymplastic Trans Vessels (xylem) hair Lower epidermis Cuticle toma Microfibril (cross section) 9 0 Guard s turgid/toma open Guard s flaccid/toma closed Radially oriented ulose microfibrils Mesophyll s toma Water molecule Transpiration Atmosphere Leaf ψ (air spaces) 7.0 MPa Water potential gradient Xylem s Water Air-water film interface Xylem sap Outside air ψ 00.0 MPa Cell wall Adhesion by hydrogen bonding Vacuole Guard (a) Changes in guard shape and stomatal opening and closing (surface view) Cohesion Cohesion by hydrogen and adhesion bonding in the xylem Water molecule oil particle Water Water uptake from soil oil ψ 0. MPa hair Trunk xylem ψ 0.6 MPa (b) Role of potassium ions () in stomatal opening and closing Ocotillo (Fouquieria splendens) Air space Endodermis Vascular cylinder (stele) Transport in the xylem Trunk xylem ψ 0.8 MPa Microfibrils in wall of mesophyll The endodermis: controlled entry to the vascular cylinder (stele) Leaf ψ ( walls).0 MPa Xylem Cuticle Oleander (Nerium oleander) Thick cuticle Upper epidermal tissue Apoplast ymplast 00 µm Companion Mesophyll (transfer) s (apoplast) ieve-tube element Plasmodesmata Trichomes Crypt toma ( hairs ) Lower epidermal tissue Phloem BundleMesophyll sheath parenchyma (a) ucrose manufactured in mesophyll s can travel via the symplast (blue arrows) to sieve-tube elements. Old man cactus (Cephalocereus senilis) igh concentration Proton pump Cotransporter Low concentration ucrose (b) A chemiosmotic mechanism is responsible for the active transport of sucrose.

5 Vessel (xylem) ieve ource tube (leaf) (phloem) Loading of sugar Bulk flow by negative pressure O Bulk flow by positive pressure ucrose O ink (storage root) Uptake of water Unloading of sugar O ucrose Recycling of water