Download AP Biology Chapter 36 Resource Acquisition and Transport in Plants

LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 36
Resource Acquisition and
Transport in Vascular Plants
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
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
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• 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
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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
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• 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
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Figure 36.2-3
CO2
H2O
O2
Light
Sugar
O2
H2O
and
minerals
CO2
• Adaptations in each species represent
compromises between enhancing _____________
and minimizing ______________ loss
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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
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• ___________________, 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
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Figure 36.3
42
16
34
21
32
24
29
11
40
19
27
3
8
6
14
13
26
5
Shoot
apical
meristem
10
2
18
Buds
31
23
15
28
1
9
4
7
20
1 mm
22
12
25
17
• 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
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Figure 36.4
Ground area
covered by plant
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
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• ________________ and ________________ also
affect light capture
• There is a _____________ between growing tall
and branching
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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
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• 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
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Figure 36.5
Roots
Fungus
Concept 36.2: Different mechanisms
transport substances over short or long
distances
• There are two major pathways through plants
– The _______________
– The _______________
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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 _______________
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• 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
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Figure 36.6
Cell wall
Apoplastic route
Cytosol
Symplastic route
Transmembrane route
Key
Plasmodesma
Plasma membrane
Apoplast
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 __________________________
___________________
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Figure 36.7
CYTOPLASM



ATP
EXTRACELLULAR FLUID
+
H+ Hydrogen ion
+
+ H+
H+
H+
H+
H+

Proton pump 

H+ 
H+

+
H+
+ +
H
+
+ H+
H+
H+
H+



H+
+ H+
+ Sucrose
+ (neutral solute)
K+
K+



+
+ H+
H+
+
+
+
+
Nitrate
H+
H+
Potassium ion
K+
K+
K+

Ion channel 
(c) H+ and cotransport of ions
+
H+
+
+ H+
H+
H+


H+NO3
cotransporter 
H+
(b) H+ and cotransport of neutral
solutes
H+
H+


H+/sucrose

cotransporter
K+
H+
+
H+
H+
(a) H+ and membrane potential
K+
+
+
(d) Ion channels
Figure 36.7a
CYTOPLASM
ATP

EXTRACELLULAR FLUID
+

+

+
H+
H+
Hydrogen ion
H+
H+
H+
H+

Proton pump 
+
+
(a) H+ and membrane potential
H+
H+
• Plant cells use the energy of _______________to
cotransport other solutes by active transport
© 2011 Pearson Education, Inc.
Figure 36.7b
H+
H+

+

+

+
H+
H+
H+
H+
H+
H+


H+/sucrose
cotransporter 
H+
H+
+ H+
+
Sucrose
+
(neutral solute)
(b) H+ and cotransport of neutral solutes
Figure 36.7c
H+
H+

+

+

+ H+
H+
H+
H+
H+

+

+ H+
H+NO3
cotransporter 
+
(c) H+ and cotransport of ions
H+
Nitrate
H+
H+
• Plant cell membranes have ________________
that allow only certain ions to pass
© 2011 Pearson Education, Inc.
Figure 36.7d
K+
K+
K+

+

+

+
Potassium ion
K+
K+
K+
Ion channel
(d) Ion channels
K+

+

+
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
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• __________________ 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 __________
________
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• 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
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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 ________________
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• __________________ (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
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• 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
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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
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• 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
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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
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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
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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 _________________________
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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
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• The concentration of essential minerals is greater
in the _______________ than soil because of
_________________________
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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
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• 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
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Figure 36.10
Casparian strip
Pathway along Endodermal
cell
apoplast
Pathway
through
symplast
Plasma
membrane
Casparian strip
Apoplastic
route
Symplastic
route
Vessels
(xylem)
Root
hair
Epidermis
Endodermis
Cortex
Vascular cylinder
(stele)
• 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 ________________________
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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?
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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
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• _____________________is relatively weak and is
a minor mechanism of xylem bulk flow
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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
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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 _________
______________________
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• This negative pressure ______________water in
the xylem into the leaf
• The _____________________ on xylem sap is
transmitted from leaves to roots
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Figure 36.12
Cuticle
Xylem
Upper
epidermis
Mesophyll
Air
space
Microfibrils in
cell wall of
mesophyll cell
Lower
epidermis
Cuticle
Stoma
Microfibril
Water Air-water
(cross section) film interface
Figure 36.13
Xylem sap
Outside air 
 100.0 MPa
Mesophyll cells
Stoma
Leaf  (air spaces)
 7.0 MPa
Trunk xylem 
 0.8 MPa
Water potential gradient
Leaf  (cell walls)
 1.0 MPa
Water molecule
Transpiration Atmosphere
Xylem
cells
Adhesion by
hydrogen bonding
Cell wall
Cohesion and
adhesion in
the xylem
Cohesion by
hydrogen bonding
Water molecule
Root hair
Trunk xylem 
 0.6 MPa
Soil 
 0.3 MPa
Soil particle
Water uptake
from soil
Water
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
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• 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
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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 _______________________
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• 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 _________________
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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
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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
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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
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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
K
H2O
H2O
H2O
H2O
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
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Figure 36.15b
Guard cells turgid/
Stoma open
H 2O
K
Guard cells flaccid/
Stoma closed
H 2O
H 2O
H 2O
H 2O
H 2O
H 2O
H2O
H 2O
H 2O
(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
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• 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
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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
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Adaptations That Reduce Evaporative
Water Loss
• ____________are plants adapted to arid climates
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Figure 36.16
Ocotillo
(leafless)
Oleander leaf cross section
Cuticle
Upper epidermal tissue
100 m
Ocotillo after
heavy rain
Oleander
flowers
Trichomes Crypt Stoma
(“hairs”)
Ocotillo leaves
Old man cactus
Lower epidermal
tissue
• 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 _______________
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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 ____________
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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 _________________
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• 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
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Figure 36.17
Key
Apoplast
Symplast
Mesophyll cell
Companion
(transfer) cell
Cell walls (apoplast)
Plasma membrane
High H concentration
H
Proton
pump
Sieve-tube
element
Cotransporter
S
Plasmodesmata
ATP
BundleMesophyll cell sheath cell
(a)
Phloem
parenchyma cell
H
Low H concentration
(b)
H
Sucrose
S
• 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
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Bulk Flow by Positive Pressure: The
Mechanism of Translocation in Angiosperms
• Phloem sap moves through a sieve tube by _____
_____________ driven by positive pressure called
________________
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Figure 36.18
Sieve Source cell
tube (leaf)
(phloem)
Vessel
(xylem)
H2O
1
1 Loading of sugar
Sucrose
H2O
Bulk flow by negative pressure
Bulk flow by positive pressure
2
2 Uptake of water
3 Unloading of sugar
Sink cell
(storage
root)
4 Water recycled
3
4
H2O
Sucrose
• 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
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Figure 36.19
EXPERIMENT
25 m
Sievetube
element
Sap
droplet
Aphid feeding
Stylet
Sap droplet
Stylet in sieve-tube Separated stylet
exuding sap
element
Concept 36.6: The symplast is highly
dynamic
• The __________________ is a living tissue and is
responsible for dynamic changes in plant transport
processes
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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
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Phloem: An Information Superhighway
• Phloem is a “superhighway” for ____________
______________ of macromolecules and viruses
• ___________________ communication helps
integrate functions of the whole plant
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Electrical Signaling in the Phloem
• The phloem allows for rapid ______________
____________between widely separated organs
– For example, ________________ in the sensitive
plant (Mimosa pudica)
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