Resource Acquisition and Transport in Vascular Plants Chapter 36 Resource Acquisition and Transport in Vascular Plants

Overview: Underground Plants Stone plants (Lithops) are adapted to life in the desert Two __________________leaf tips are exposed above ground; the rest of the plant lives below ground © 2011 Pearson Education, Inc.

The success of plants depends on their ability to gather and conserve _________________from their environment The _______________________is central to the integrated functioning of the whole plant © 2011 Pearson Education, Inc.

Concept 36.1: Adaptations for acquiring resources were key steps in the evolution of vascular plants The _______ ancestors of land plants absorbed water, minerals, and CO2 directly from the surrounding ___________ Early ___________________ land plants lived in shallow water and had ___________ shoots ____________________ favored taller plants with flat appendages, multicellular branching roots, and efficient transport © 2011 Pearson Education, Inc.

_______________ transports water and minerals from roots to shoots The evolution of _________________ in land plants made possible the long-distance transport of water, minerals, and products of photosynthesis _______________ transports water and minerals from roots to shoots _______________ transports photosynthetic products from sources to sinks © 2011 Pearson Education, Inc.

CO2 O2 Light Sugar H2O O2 H2O and minerals CO2 Figure 36.2-3 Figure 36.2 An overview of resource acquisition and transport in a vascular plant. O2 H2O and minerals CO2

Adaptations in each species represent compromises between enhancing _____________ and minimizing ______________ loss © 2011 Pearson Education, Inc.

Shoot Architecture and Light Capture __________ serve as conduits for water and nutrients and as supporting structures for leaves There is generally a ______________ correlation between water availability and leaf size © 2011 Pearson Education, Inc.

___________________, the arrangement of leaves on a stem, is specific to each species Most angiosperms have _________________ with leaves arranged in a spiral The angle between leaves is 137.5 and likely minimizes _________________ of lower leaves © 2011 Pearson Education, Inc.

Figure 36.3 24 32 42 29 40 16 11 19 21 27 3 34 8 6 14 13 26 Shoot apical meristem 1 5 22 9 18 Buds 10 4 2 31 17 7 12 Figure 36.3 Emerging phyllotaxy of Norway spruce. 23 15 20 25 28 1 mm

Light absorption is affected by the ____________, the ratio of total upper leaf surface of a plant divided by the surface area of land on which it grows _________________________ is the shedding of lower shaded leaves when they respire more than photosynthesize © 2011 Pearson Education, Inc.

Ground area covered by plant Figure 36.4 Ground area covered by plant Figure 36.4 Leaf area index. Plant A Leaf area  40% of ground area (leaf area index  0.4) Plant B Leaf area  80% of ground area (leaf area index  0.8)

____________________ affects light absorption In low-light conditions, __________________ capture more sunlight In sunny conditions, ______________________ are less damaged by sun and allow light to reach lower leaves © 2011 Pearson Education, Inc.

________________ and ________________ also affect light capture There is a _____________ between growing tall and branching © 2011 Pearson Education, Inc.

Root Architecture and Acquisition of Water and Minerals _________ is a resource mined by the root system Taproot systems anchor plants and are characteristic of ____________ and ___________ _______________ can adjust to local conditions For example, roots branch more in a pocket of high nitrate than low nitrate Roots are _______________ with other roots from the same plant than with roots from different plants © 2011 Pearson Education, Inc.

Mutualisms with fungi helped plants ___________ Roots and the hyphae of soil fungi form mutualistic associations called _______________ Mutualisms with fungi helped plants ___________ Mycorrhizal fungi increase the _______________ for absorbing water and minerals, especially phosphate © 2011 Pearson Education, Inc.

Figure 36.5 Roots Figure 36.5 A mycorrhiza, a mutualistic association of fungus and roots. Fungus

Concept 36.2: Different mechanisms transport substances over short or long distances There are two major pathways through plants The _______________ © 2011 Pearson Education, Inc.

The Apoplast and Symplast: Transport Continuums The ______________ consists of everything external to the plasma membrane It includes _______________, ______________, and the interior of _____________ and ________ The _________ consists of the cytosol of the living cells in a plant, as well as the _______________ © 2011 Pearson Education, Inc.

Three transport routes for water and solutes are The ____________ route, through cell walls and extracellular spaces The _______________ route, through the cytosol The _______________ route, across cell walls © 2011 Pearson Education, Inc.

Cell wall Apoplastic route Cytosol Symplastic route Figure 36.6 Cell wall Apoplastic route Cytosol Symplastic route Transmembrane route Key Figure 36.6 Cell compartments and routes for short-distance transport. Plasmodesma Apoplast Plasma membrane Symplast

Short-Distance Transport of Solutes Across Plasma Membranes Plasma membrane permeability controls _______ _______________________ of substances Both _________________ and ______________ occur in plants In plants, membrane potential is established through pumping ____ by _________________ In animals, membrane potential is established through pumping __________________________ ___________________ © 2011 Pearson Education, Inc.

Figure 36.7 Solute transport across plant cell plasma membranes. CYTOPLASM EXTRACELLULAR FLUID (a) H+ and membrane potential  + ATP  H+ + Hydrogen ion  + H+ H+ H+ H+ H+  + H+ Proton pump H+  +  + (b) H+ and cotransport of neutral solutes S H+ H+  + H+ H+  + H+ H+ S H+ S H+ H+ H+ S S  + S H+  H+/sucrose cotransporter + Sucrose (neutral solute)  +  + (c) H+ and cotransport of ions H+ H+ NO3  + NO3  + H+ H+ H+ H+ Nitrate H+ NO3 H+ Figure 36.7 Solute transport across plant cell plasma membranes. NO3  + NO3 NO3  + H+ H+NO3 cotransporter H+  + H+  + (d) Ion channels K+ Potassium ion  + K+ K+  + K+ K+ K+ K+  + Ion channel  +

CYTOPLASM EXTRACELLULAR FLUID Hydrogen ion Proton pump  + H+  + ATP Figure 36.7a CYTOPLASM EXTRACELLULAR FLUID  + H+  + Hydrogen ion ATP  + H+ H+ H+ H+ H+ H+  + Figure 36.7 Solute transport across plant cell plasma membranes. Proton pump H+  + (a) H+ and membrane potential

Plant cells use the energy of _______________to cotransport other solutes by active transport © 2011 Pearson Education, Inc.

H+/sucrose cotransporter Sucrose (neutral solute) Figure 36.7b  + H+ S H+  + H+ H+  + H+ H+ H+ S S H+ H+ H+ S S S  + H+  Figure 36.7 Solute transport across plant cell plasma membranes. + H+/sucrose cotransporter Sucrose (neutral solute)  + (b) H+ and cotransport of neutral solutes

Nitrate H+NO3 cotransporter  + H+ H+ NO3  + NO3  H+ + H+ H+ H+ Figure 36.7c  + H+ H+ NO3  + NO3  + H+ H+ H+ H+ Nitrate H+ H+ NO3 NO3  NO3 + NO3  + H+ Figure 36.7 Solute transport across plant cell plasma membranes. H+NO3 cotransporter H+  H+ + (c) H+ and cotransport of ions

Plant cell membranes have ________________ that allow only certain ions to pass © 2011 Pearson Education, Inc.

 + K+ Potassium ion  + K+  K+ + K+ K+ K+ K+  + Ion channel  + Figure 36.7d  + K+ Potassium ion  + K+  K+ + K+ K+ K+ K+  + Ion channel Figure 36.7 Solute transport across plant cell plasma membranes.  + (d) Ion channels

Short-Distance Transport of Water Across Plasma Membranes To survive, plants must balance _____________ uptake and loss ______________ determines the net uptake or water loss by a cell and is affected by solute concentration and pressure © 2011 Pearson Education, Inc.

Water potential determines the __________ of movement of water __________________ is a measurement that combines the effects of solute concentration and pressure Water potential determines the __________ of movement of water Water flows from regions of _________ water potential to regions of _________ water potential Potential refers to water’s capacity to __________ ________ © 2011 Pearson Education, Inc.

Ψ = ___ MPa for pure water at sea level and at room temperature Water potential is abbreviated as Ψ and measured in a unit of pressure called the _______________ Ψ = ___ MPa for pure water at sea level and at room temperature © 2011 Pearson Education, Inc.

How Solutes and Pressure Affect Water Potential Both ___________ and ____________________ affect water potential This is expressed by the water potential equation: _________________ The _____________________ (ΨS) of a solution is directly proportional to its molarity Solute potential is also called ________________ © 2011 Pearson Education, Inc.

__________________ (ΨP) is the physical pressure on a solution __________________ is the pressure exerted by the plasma membrane against the cell wall, and the cell wall against the protoplast The ____________ is the living part of the cell, which also includes the plasma membrane © 2011 Pearson Education, Inc.

Consider a U-shaped tube where the two arms are separated by a membrane permeable only to water Water moves in the direction from ________ water potential to __________ water potential © 2011 Pearson Education, Inc.

Water Movement Across Plant Cell Membranes _______________affects uptake and loss of water by plant cells If a _____________ cell is placed in an environment with a higher solute concentration, the cell will lose water and undergo plasmolysis _________________ occurs when the protoplast shrinks and pulls away from the cell wall © 2011 Pearson Education, Inc.

If a flaccid cell is placed in a solution with a lower solute concentration, the cell will gain water and become _______________ Turgor loss in plants causes ____________, which can be reversed when the plant is watered © 2011 Pearson Education, Inc.

Aquaporins: Facilitating Diffusion of Water ________________ are transport proteins in the cell membrane that allow the passage of water These affect the _____________ of water movement across the membrane © 2011 Pearson Education, Inc.

Long-Distance Transport: The Role of Bulk Flow Efficient long distance transport of fluid requires ______________, the movement of a fluid driven by pressure Water and solutes move together through tracheids and vessel elements of _________, and sieve-tube elements of ___________________ Efficient movement is possible because mature tracheids and vessel elements have _______ __________, and sieve-tube elements have ______________________in their cytoplasm © 2011 Pearson Education, Inc.

Concept 36.3: 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 _________________________ © 2011 Pearson Education, Inc.

Absorption of Water and Minerals by Root Cells Most water and mineral absorption occurs near root tips, where ______________are located and the ______________ is permeable to water Root hairs account for much of the __________ ______________of roots After soil solution enters the roots, the extensive surface area of ________________________ enhances uptake of water and selected minerals © 2011 Pearson Education, Inc.

The concentration of essential minerals is greater in the _______________ than soil because of _________________________ © 2011 Pearson Education, Inc.

Transport of Water and Minerals into the Xylem The _________________is the innermost layer of cells in the root cortex It surrounds the __________________ and is the last checkpoint for _____________________ of minerals from the cortex into the vascular tissue © 2011 Pearson Education, Inc.

Water can cross the cortex via the __________ or _________________ The waxy _______________________ 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 ____________________ to enter the vascular cylinder © 2011 Pearson Education, Inc.

Pathway along apoplast Figure 36.10 Casparian strip Endodermal cell Pathway along apoplast Pathway through symplast Plasma membrane Casparian strip Apoplastic route Figure 36.10 Transport of water and minerals from root hairs to the xylem. Vessels (xylem) Symplastic route Root hair Epidermis Endodermis Vascular cylinder (stele) Cortex

The _________________regulates and transports needed minerals from the soil into the xylem Water and minerals move from the protoplasts of ___________________ into their _____________ Diffusion and active transport are involved in this movement from _____________ to ___________ Water and minerals now enter the ___________ and ________________________ © 2011 Pearson Education, Inc.

Bulk Flow Transport via the Xylem ___________________, water and dissolved minerals, is transported from roots to leaves by bulk flow The transport of xylem sap involves ________________, the evaporation of water from a plant’s surface Transpired water is ______________as water travels up from the roots Is sap pushed up from the roots, or pulled up by the leaves? © 2011 Pearson Education, Inc.

Pushing Xylem Sap: Root Pressure At night root cells continue pumping mineral ions into the xylem of the vascular cylinder, __________ the water potential Water flows in from the root cortex, generating ________________________ Root pressure sometimes results in ______________, the exudation of water droplets on tips or edges of leaves © 2011 Pearson Education, Inc.

_____________________is relatively weak and is a minor mechanism of xylem bulk flow © 2011 Pearson Education, Inc.

Pulling Xylem Sap: The Cohesion-Tension Hypothesis According to the _________________________, transpiration and water cohesion pull water from shoots to roots Xylem sap is normally under ________________, or tension © 2011 Pearson Education, Inc.

Transpirational Pull Water vapor in the airspaces of a leaf diffuses down its water potential gradient and exits the leaf via __________________ As water evaporates, the air-water interface __________________ further into the mesophyll cell walls The surface tension of water creates a _________ ______________________ © 2011 Pearson Education, Inc.

This negative pressure ______________water in the xylem into the leaf The _____________________ on xylem sap is transmitted from leaves to roots © 2011 Pearson Education, Inc.

Microfibrils in cell wall of mesophyll cell Mesophyll Air space Figure 36.12 Cuticle Xylem Upper epidermis Microfibrils in cell wall of mesophyll cell Mesophyll Air space Figure 36.12 Generation of transpirational pull. Lower epidermis Cuticle Stoma Microfibril (cross section) Water film Air-water interface

Outside air   100.0 MPa Leaf  (air spaces)  7.0 MPa Figure 36.13 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 36.13 Ascent of xylem sap. Water molecule Root hair Trunk xylem   0.6 MPa Soil particle Soil  Water Water uptake from soil  0.3 MPa

Adhesion and Cohesion in the Ascent of Xylem Sap Water molecules are attracted to _____________in xylem cell walls through adhesion ________________ of water molecules to xylem cell walls helps offset the force of gravity © 2011 Pearson Education, Inc.

Water molecules are attracted to each other through cohesion _________________ makes it possible to pull a column of xylem sap Thick secondary walls prevent _______________ and ________________ from collapsing under negative pressure Drought stress or freezing can cause __________, the formation of a water vapor pocket by a break in the chain of water molecules © 2011 Pearson Education, Inc.

Xylem Sap Ascent by Bulk Flow: A Review The movement of xylem sap against gravity is maintained by the _________________________ ________________________ Bulk flow is driven by a ____________________ ______________ at opposite ends of xylem tissue Bulk flow is driven by evaporation and does not require energy from the plant; like photosynthesis it is _______________________ © 2011 Pearson Education, Inc.

Bulk flow differs from ______________ It is driven by differences in _______________, not solute potential It occurs in hollow ________________, not across the membranes of living cells It moves the entire solution, not just water or solutes It is much _________________ © 2011 Pearson Education, Inc.

Concept 36.4: The rate of transpiration is regulated by stomata Leaves generally have broad surface areas and _____________ surface-to-volume ratios These characteristics increase ______________ and increase _______________ through stomata _______________ help balance water conservation with gas exchange for photosynthesis © 2011 Pearson Education, Inc.

Stomata: Major Pathways for Water Loss About _________ of the water a plant loses escapes through stomata Each stoma is flanked by a pair of _____________ , which control the diameter of the stoma by changing shape Stomatal density is under ______ and __________________ control © 2011 Pearson Education, Inc.

Mechanisms of Stomatal Opening and Closing Changes in ___________ open and close stomata When ___________, guard cells bow outward and the pore between them opens When ______________, guard cells become less bowed and the pore closes © 2011 Pearson Education, Inc.

Guard cells turgid/ Stoma open Guard cells flaccid/ Stoma closed Figure 36.15 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 36.15 Mechanisms of stomatal opening and closing. H2O K H2O H2O H2O H2O H2O (b) Role of potassium in stomatal opening and closing

This results primarily from the reversible uptake and loss of ____________(K) by the guard cells © 2011 Pearson Education, Inc.

Guard cells turgid/ Stoma open Guard cells flaccid/ Stoma closed Figure 36.15b Guard cells turgid/ Stoma open Guard cells flaccid/ Stoma closed H2O H2O H2O H2O H2O K H2O H2O H2O Figure 36.15 Mechanisms of stomatal opening and closing. H2O H2O (b) Role of potassium in stomatal opening and closing

Stimuli for Stomatal Opening and Closing Generally, stomata _________ during the day and ___________ at night to minimize water loss Stomatal opening at dawn is triggered by _____________ An internal “__________” in guard cells All eukaryotic organisms have internal clocks; _____________________ are 24-hour cycles © 2011 Pearson Education, Inc.

Drought, high temperature, and wind can cause stomata to ______________during the daytime The hormone ___________________ is produced in response to water deficiency and causes the closure of stomata © 2011 Pearson Education, Inc.

Effects of Transpiration on Wilting and Leaf Temperature Plants lose a large amount of water by _____________________ If the lost water is not replaced by sufficient transport of water, the plant will lose water and _____________ Transpiration also results in ________________, which can lower the temperature of a leaf and prevent _____________________ of various enzymes involved in photosynthesis and other metabolic processes © 2011 Pearson Education, Inc.

Adaptations That Reduce Evaporative Water Loss ____________are plants adapted to arid climates © 2011 Pearson Education, Inc.

Oleander leaf cross section Figure 36.16 Ocotillo (leafless) Oleander leaf cross section Cuticle Upper epidermal tissue Ocotillo after heavy rain Oleander flowers 100 m Trichomes (“hairs”) Crypt Stoma Lower epidermal tissue Figure 36.16 Some xerophytic adaptations. Ocotillo leaves Old man cactus

Others have ________________ that reduce the rate of transpiration Some desert plants complete their life cycle during the _________________season Others have ________________ that reduce the rate of transpiration Some plants use a specialized form of photosynthesis _________________________ _____________________ where stomatal gas exchange occurs at _______________ © 2011 Pearson Education, Inc.

Concept 36.5: Sugars are transported from sources to sinks via the phloem The products of photosynthesis are transported through phloem by the process of ____________ © 2011 Pearson Education, Inc.

Movement from Sugar Sources to Sugar Sinks In angiosperms, ________________are the conduits for translocation _______________ is an aqueous solution that is high in sucrose It travels from a sugar source to a sugar sink A ________________is an organ that is a net producer of sugar, such as mature ____________ A ___________ is an organ that is a net consumer or storer of sugar, such as a _________________ © 2011 Pearson Education, Inc.

A storage organ can be both a sugar sink in ____________ and sugar source in ___________ Sugar must be ______________ into sieve-tube elements before being exported to sinks Depending on the species, sugar may move by _________________ or both symplastic and __________________ pathways _____________________ enhance solute movement between the apoplast and symplast © 2011 Pearson Education, Inc.

Companion (transfer) cell High H concentration Cotransporter Figure 36.17 Key Apoplast Symplast Companion (transfer) cell High H concentration Cotransporter Mesophyll cell Proton pump H Cell walls (apoplast) Sieve-tube element S Plasma membrane Plasmodesmata Figure 36.17 Loading of sucrose into phloem. ATP Sucrose H H S Bundle- sheath cell Phloem parenchyma cell Mesophyll cell Low H concentration (a) (b)

In many plants, phloem loading requires _________ _________________ __________________and ______________ of sucrose and H+ enable the cells to accumulate sucrose At the sink, _____________________diffuse from the phloem to sink tissues and are followed by water © 2011 Pearson Education, Inc.

Bulk Flow by Positive Pressure: The Mechanism of Translocation in Angiosperms Phloem sap moves through a sieve tube by _____ _____________ driven by positive pressure called ________________ © 2011 Pearson Education, Inc.

1 Loading of sugar 2 Uptake of water 3 Unloading of sugar 4 Figure 36.18 Sieve tube (phloem) Source cell (leaf) Vessel (xylem) 1 Loading of sugar H2O 1 Sucrose H2O 2 2 Uptake of water Bulk flow by positive pressure Bulk flow by negative pressure 3 Unloading of sugar Figure 36.18 Bulk flow by positive pressure (pressure flow) in a sieve tube. Sink cell (storage root) 4 Water recycled 4 3 Sucrose H2O

The pressure flow hypothesis explains why phloem sap always flows from _______________ Experiments have built a strong case for pressure flow as the mechanism of ________________ in angiosperms _____________________ is the dropping of sugar sinks such as flowers, seeds, or fruits © 2011 Pearson Education, Inc.

Stylet in sieve-tube element Separated stylet exuding sap Figure 36.19 EXPERIMENT 25 m Sieve- tube element Sap droplet Figure 36.19 Inquiry: Does phloem sap contain more sugar near sources than sinks? Stylet Sap droplet Aphid feeding Stylet in sieve-tube element Separated stylet exuding sap

Concept 36.6: The symplast is highly dynamic The __________________ is a living tissue and is responsible for dynamic changes in plant transport processes © 2011 Pearson Education, Inc.

Changes in Plasmodesmata ____________________ can change in permeability in response to turgor pressure, cytoplasmic calcium levels, or cytoplasmic pH Plant viruses can cause plasmodesmata to __________ so viral RNA can pass between cells © 2011 Pearson Education, Inc.

Phloem: An Information Superhighway Phloem is a “superhighway” for ____________ ______________ of macromolecules and viruses ___________________ communication helps integrate functions of the whole plant © 2011 Pearson Education, Inc.

Electrical Signaling in the Phloem The phloem allows for rapid ______________ ____________between widely separated organs For example, ________________ in the sensitive plant (Mimosa pudica) © 2011 Pearson Education, Inc.