Plant Transport - PowerPoint Presentation

Slide1

Plant TransportSlide2

Plants

Plant:

terrestrial (mostly), multicellular, photoautotrophic, eukaryote, true tissues and organsSlide3

Plant Structure

Tissue Basic Tissue Types:

pg

717

- give rise to specialized cells

Dermal - outer coat

Vascular – transport tubes

Ground – between Dermal and VascularSlide4

Basic Tissue Layout

Dermal

Ground

VascularSlide5

Dermal

tissue

Ground

tissue

Vascular

tissueSlide6

Dermal Tissue

Epidermis

Function:

protection: secretes the cuticle, forms prickles and root hairs

Slide7

Thorns, Spines and Prickles

Based on where they originate

Thorns – modified stems

Spines – modified leaves

Prickles – modified epidermal cellsSlide8

ThornSlide9

SpineSlide10

Prickle

Rose “thorns” are prickles

 “A rose between two prickles.” Slide11

Vascular Tissue

Xylem:

Water conducting – unidirectional (up)

Dead at maturity –

pg

719

Phloem:

Sugar conduction – bidirectional

Sieve Tube Members

: alive and functional – lack many organelles

Companion Cells: connected to Sieve Tube Members by plasmodesmata – supports the STM with its organelle functionSlide12

XylemSlide13

PhloemSlide14

Figure. 35.9

WATER-CONDUCTING CELLS OF THE XYLEM

Vessel

Tracheids

100

m

Tracheids and vessels

Vessel

element

Vessel elements with

partially perforated

end walls

Pits

Tracheids

SUGAR-CONDUCTING CELLS OF THE PHLOEM

Companion cell

Sieve-tube

member

Sieve-tube members:

longitudinal view

Sieve

plate

Nucleus

Cytoplasm

Companion

cell

30

m

15

m

Slide15

Ground Tissue

Occupies the space

between the vascular tissue and the dermal tissue

Functions:

Storage – roots and stems

Support – stems

Photosynthesis – leaves and some stemsSlide16

Types of Ground Tissue

1.Parenchyma: undifferentiated, thin cell walls (still flexible)

– used for metabolism and photosynthesis

Ex:

Pallisade

and Spongy Mesophyll of leaf

Potato, Fruit pulp

2. Collenchyma: unevenly thickened cell walls

– support young parts of plants – no lignin, but stronger than parenchyma

Ex: “Strings” in celery

3. Sclerenchyma: highly thickened cell walls

– lignified – support mature tissue – hard and dead

Two types: Fibers and Sclerids Ex: Walnut Shell, Stone Cells in PearsSlide17

Figure 35.9

Parenchyma cells

60

m

PARENCHYMA CELLS

80

m

Cortical parenchyma cells

COLLENCHYMA CELLS

Collenchyma cells

SCLERENCHYMA CELLS

Cell wall

Sclereid cells

in pear

25

m

Fiber cells

5

m

Slide18

Plant Parts: Roots, Stems and Leaves

Roots:

Functions:

-

absorb water, nutrients and minerals

-

anchor plant in soil

-

store food and water

-

support the plantSlide19

(a) Prop roots

(b) Storage roots

(c) “Strangling” aerial

roots

(d) Buttress roots

(e) PneumatophoresSlide20

Increasing Absorption

Root hairs

– extensions of the

epidermis

Branching roots

– lateral roots

MycorrhizaeSlide21

Root Structure

Outside

 In

Epidermis (D)

Cortex (G) – storage and nutrient transfer

Endodermis (G

)

–

separates ground and vascular tissue – important for water transfer

Pericycle

(V) – forms the lateral roots

Stele (Xylem and Phloem) (V)Slide22

Cortex

Vascular

cylinder

Endodermis

Pericycle

Core of

parenchyma

cells

Xylem

50

m

Endodermis

Pericycle

Xylem

Phloem

Key

100

m

Vascular

Ground

Dermal

Phloem

Transverse section of a root with parenchyma

in the center.

The stele of many monocot roots

is a vascular cylinder with a core of parenchyma

surrounded by a ring of alternating xylem and phloem.

(b)

Transverse section of a typical root.

In the

roots of typical gymnosperms and eudicots, as

well as some monocots, the stele is a vascular

cylinder consisting of a lobed core of xylem

with phloem between the lobes.

(a)

100

m

EpidermisSlide23

Eudicot

Root – Cross Section

From: http://www.inclinehs.org/smb/Sungirls/images/dicot_stem.JPGSlide24

Monocot Root Cross Section

From: http://www.inclinehs.org/smb/Sungirls/images/monocot_stem.JPGSlide25

Monocot Root Vascular CylinderSlide26

Monocot Stele

From: http://www.botany.hawaii.edu/faculty/webb/BOT201/Angiosperm/MagnoliophytaLab99/SmilaxRotMaturePhloemXylem300Lab.jpgSlide27

Growth of Lateral Roots

Cortex

Vascular

cylinder

Epidermis

Lateral root

100

m

1

2

3

4

Emerging

lateral

rootSlide28

Eudicot & Monocot Roots - External

Eudicot –

tap root

Monocot –

fibrous rootsSlide29

Stems

Function:

-

support leaves and flowers

-

photosynthesis (non-woody plants – herbaceous)

-

storage: food (tubers – potato) and water (cactus)Slide30

Stem Structure

Nodes: points where leaves are/were attached

Internodes: area of growth between the nodes

Bud: Developing leaves

Terminal/Apical Bud: end of a branch

Lateral/Axillary Bud: lateral growth – between leaf petiole (“stem” of leaf) and main stem

Bud Scale Scars: Sites of old bud scales (protective layers around the buds) - # of bud scale scars indicates the age of the stem

Leaf Scars: Sites where leaves were attached to the stem

Lenticles

: “bumps” of cork lined pores that allow for oxygen exchange in the stem Slide31

This year’s growth

(one year old)

Last year’s growth

(two years old)

Growth of two

years ago (three

years old)

One-year-old side

branch formed

from axillary bud

near shoot apex

Scars left by terminal

bud scales of previous

winters

Leaf scar

Leaf scar

Stem

Leaf scar

Bud scale

Axillary buds

Internode

Node

Terminal budSlide32

Stem: Internal Anatomy

Epidermis

Ground Tissue

Pith

Vascular Bundles

Contain Xylem and Phloem

May contain: Vascular Cambium, Cork Cambium, Sclerenchyma Slide33

Monocot Stem Structure

Ground

tissue

Epidermis

Vascular

bundles

1 mm

(b) A monocot stem.

A monocot stem (maize) with vascular

bundles scattered throughout the ground tissue. In such an

arrangement, ground tissue is not partitioned into pith and

cortex. (LM of transverse section) Slide34

Monocot Stem Vascular Bundles

Xylem

PhleomSlide35

Monocot Stem Vascular Bundle

From: http://iweb.tntech.edu/mcaprio/stem_dicot_400X_cs_E.jpgSlide36

Eudicot

Stem Structure

Xylem

Phloem

Sclerenchyma

(fiber cells)

Ground tissue

connecting

pith to cortex

Pith

Epidermis

Vascular

bundle

Cortex

Key

Dermal

Ground

Vascular

1 mm

(a) A eudicot stem.

A eudicot stem (sunflower), with

vascular bundles forming a ring. Ground tissue toward

the inside is called pith, and ground tissue toward the

outside is called cortex. (LM of transverse section) Slide37

Eudicot

Stem Cross Section

From: http://plantphys.info/plant_physiology/images/stemcs.jpgSlide38

Eudicot

Stem Vascular Bundle

Xylem

Phloem

Vascular Cambium

SclerenchymaSlide39

Leaves

Functions:

-

photosynthesis

-

storage (succulent leaves, Aloe)

-

protection: spines, toxins, trichomes

-

reproduction: flowers (modified leaves)Slide40

Leaves

Functions:

-

photosynthesis

-

storage (succulent leaves, Aloe)

-

protection: spines, toxins,

trichomes

-

reproduction: flowers (modified leaves)Slide41

Leaves: External Structure

Blade

Petiole

Stipule

Axillary Bud

VeinsSlide42

Stipule – growth at the base of petioleSlide43

Leaves: Internal Structure

- Cuticle

- Upper Epidermis (

Adaxil

)

- Mesophyll:

- Palisade Layer

- Spongy Layer

- Air Spaces

- Vascular Bundle

- Bundle Sheath Cells

- Xylem and Phloem

-Lower Epidermis (Abaxil) - Stomata - Guard Cells- Cuticle Slide44

Key

to labels

Dermal

Ground

Vascular

Guard

cells

Stomatal pore

Epidermal

cell

50 µm

Surface view of a spiderwort

(

Tradescantia

) leaf (LM)

(b)

Cuticle

Sclerenchyma

fibers

Stoma

Upper

epidermis

Palisade

mesophyll

Spongy

mesophyll

Lower

epidermis

Cuticle

Vein

Guard

cells

Xylem

Phloem

Guard

cells

Bundle-

sheath

cell

Cutaway drawing of leaf tissues

(a)

Vein

Air spaces

Guard cells

100 µm

Transverse section of a lilac

(

Syringa

) leaf (LM)

(c)

Figure 35.17a–cSlide45

Leaf MesophyllSlide46

Leaf StomataSlide47

Plant TransportSlide48

Turgor loss in plants causes wilting

Which can be reversed when the plant is watered

Figure 36.7Slide49

Plant Transport of Solutes

Proton Pumps

: Active transport of

H+ out of the cell

Builds

proton gradient

Functions: provides potential for the

COTRANSPORT

of materials across the membrane with the H+

CYTOPLASM

EXTRACELLULAR FLUID

ATP

H

+

H

+

H

+

H

+

H

+

H

+

H

+

H

+

Proton pump generates

membrane potential

and H

+

gradient.

–

–

–

–

–

+

+

+

+

+Slide50

Figure 36.4b

H

+

H

+

H

+

H

+

H

+

H

+

H

+

H

+

H

+

H

+

H

+

H

+

NO

3

–

NO

3

–

NO

3

–

NO

3

–

NO

3

–

NO

3

–

–

–

–

+

+

+

–

–

–

+

+

+

NO

3

–

(b) Cotransport of anions

H

+

of through a

cotransporter.

Cell accumulates

anions (

, for

example) by

coupling their

transport to the

inward diffusion

H

+

H

+

H

+

H

+

H

+

H

+

H

+

H

+

H

+

H

+

S

S

S

S

S

Plant cells can

also accumulate a

neutral solute,

such as sucrose

( ), by

cotransporting

down the

steep proton

gradient.

S

H

+

–

–

–

+

+

+

–

–

+

+

–

Figure 36.4c

H

+

H

+

S

+

–

(c) Contransport of a neutral solute Slide51

Water Flow from Cell to Cell

Water moves between three major compartments of the plant cell.

Vacuole

– surrounded by

Tonoplast

Cytosol

– surrounded by the

Cell Membrane

Cell Wall – hydrophilic cellulose – absorbs water

Vacuole

Tonoplast

Cytosol

Cell Membrane

Cell WallSlide52

Three compartments make up three major pathways of transport of water from cell to cell.

Apoplastic

Route

: movement of water and solutes

through the cell walls

Symplastic

Route

: transfer of materials from

cytosol to cytosol via

plasmodesmata

Transmembrane Route: movement of water

through the walls and cell membranes Slide53

Key

Symplast

Apoplast

The symplast is the

continuum of

cytosol connected

by plasmodesmata.

The apoplast is

the continuum

of cell walls and

extracellular

spaces.

Apoplast

Transmembrane route

Symplastic route

Apoplastic route

Symplast

Transport routes between cells.

At the tissue level, there are three passages:

the transmembrane, symplastic, and apoplastic routes. Substances may transfer

from one route to another.

(b)

Figure 36.8bSlide54

Importance of Symplast and Apoplast

- provides the route for

lateral movement of water

from the

root epidermis to the vascular cylinder

Water Pathway:

Soil to root epidermis

In the epidermis water can pass through the cell membrane,

enter the

symplastic

route and travel to the xylemOR it can stay in the cell wall and follow the

apoplastic route to the endodermis. Slide55

Apoplastic

Barrier: Endodermis

Endodermal walls are infused with

suberin

(wax) that prevents the water from

entering the vascular cylinder

The water must

enter the cell through the cell membrane and then into the xylem

IMPORTANCE: This ensures that all the water and dissolved materials pass through at least one cell membrane before entering the xylem. Slide56

Figure 36.9

1

2

3

Uptake of soil solution by the

hydrophilic walls of root hairs

provides access to the apoplast.

Water and minerals can then

soak into the cortex along

this matrix of walls.

Minerals and water that cross

the plasma membranes of root

hairs enter the symplast.

As soil solution moves along

the apoplast, some water and

minerals are transported into

the protoplasts of cells of the

epidermis and cortex and then

move inward via the symplast.

Within the transverse and radial walls of each endodermal cell is the

Casparian strip, a belt of waxy material (purple band) that blocks the

passage of water and dissolved minerals. Only minerals already in

the symplast or entering that pathway by crossing the plasma

membrane of an endodermal cell can detour around the Casparian

strip and pass into the vascular cylinder.

Endodermal cells and also parenchyma cells within the

vascular cylinder discharge water and minerals into their

walls (apoplast). The xylem vessels transport the water

and minerals upward into the shoot system.

Casparian strip

Pathway along

apoplast

Pathway

through

symplast

Plasma

membrane

Apoplastic

route

Symplastic

route

Root

hair

Epidermis

Cortex

Endodermis

Vascular cylinder

Vessels

(xylem)

Casparian strip

Endodermal cell

4

5

2

1Slide57

Neither the

apoplastic

nor

symplastic

route is continuous to the xylem

Apoplastic

stops at the endodermis

Symplastic stops at the xylem

Since xylem cells are dead, the plasmodesmata from the symplastic route will not work so the water must exit the cells via the apoplastic route to go into the xylem wallsSlide58

Vertical Movement

Water – Xylem –

Pushing and Pulling

Hydrostatic Pushing – Root Pressure

Roots pump ions and solutes into the roots

increasing the solute concentration

Lowers the water potential resulting in an

influx of water which builds pressure

The pressure

pushes water up the xylem

Only good for short distances and may result in GUTTATION – forcible expulsion of water out of special structures called

hydathodes (can be used as a salt gland for plants that live in high saline environments)Slide59
Slide60

Transpirational Pull

Pulling water up the xylem

Transpiration: regulation of the

photosynthesis/transpiration compromise

by the guard cells and stomata

Proper gas exchange causes the loss of water

from the air spaces in the spongy mesophyll

The

drier air space pulls water our of the mesophyll

which gets the water from the xylemWater loss from the xylem pulls on the water molecules down the xylemSlide61

Evaporation causes the air-water interface to retreat farther into

the cell wall and become more curved as the rate of transpiration

increases. As the interface becomes more curved, the water film’s

pressure becomes more negative. This negative pressure, or tension,

pulls water from the xylem, where the pressure is greater.

Cuticle

Upper

epidermis

Mesophyll

Lower

epidermis

Cuticle

Water vapor

CO

2

O

2

Xylem

CO

2

O

2

Water vapor

Stoma

Evaporation

At first, the water vapor lost by

transpiration is replaced by

evaporation from the water film

that coats mesophyll cells.

In transpiration, water vapor (shown as

blue dots) diffuses from the moist air spaces of the

leaf to the drier air outside via stomata.

Airspace

Cytoplasm

Cell wall

Vacuole

Evaporation

Water film

Low rate of

transpiration

High rate of

transpiration

Air-water

interface

Cell wall

Airspace

Y

= –0.15 MPa

Y

= –10.00 MPa

3

1

2

Air-

spaceSlide62

Transpirational

pull results from the properties of

cohesion and adhesion

As one water molecule moves out of the xylem

it tugs on the water molecule behind it

because they are

bound by cohesion forces of the hydrogen bonds

between the molecules.

Water

does not move down the xylem because it is held in place by the adhesive forces between the water and the cellulose of the xylem walls. Slide63

Xylem

sap

Outside air

Y

= –100.0 MPa

Leaf

Y

(air spaces)

= –7.0 MPa

Leaf

Y

(cell walls)

= –1.0 MPa

Trunk xylem

Y

= – 0.8 MPa

Water potential gradient

Root xylem

Y

= – 0.6 MPa

Soil

Y

= – 0.3 MPa

Mesophyll

cells

Stoma

Water

molecule

Atmosphere

Transpiration

Xylem

cells

Adhesion

Cell

wall

Cohesion,

by

hydrogen

bonding

Water

molecule

Root

hair

Soil

particle

Water

Cohesion

and adhesion

in the xylem

Water uptake

from soil Slide64

Other Roles of Transpiration:

Evaporative Cooling

– helps keep leaves cooler during hot days

Factors Affecting Transpiration:

Temperature:

Hotter = more

Humidity: Higher = less

Air flow (wind): Higher = moreHormone Signals (

Abscisic Acid) – response to dry conditions: Release of hormone closes stomataSlide65

Regulation of Transpiration: Guard Cells

Regulate the size of

stomatal

openings for gas exchange – responsible for the photosynthesis/transpiration compromise

Anatomy of Guard Cell:

Eudicots

:

Kidney shaped

Monocots: Dumbbell shaped

Both: unevenly thickened cell walls (stomatal side is thicker)Slide66

20 µm

Figure 36.14

Cells flaccid/Stoma closed

Cells turgid/Stoma open

Radially oriented

cellulose microfibrils

Cell

wall

Vacuole

Guard cell

Changes in guard cell shape and stomatal opening

and closing (surface view).

Guard cells of a typical

angiosperm are illustrated in their turgid (stoma open)

and flaccid (stoma closed) states. The pair of guard

cells buckle outward when turgid. Cellulose microfibrils

in the walls resist stretching and compression in the

direction parallel to the microfibrils. Thus, the radial

orientation of the microfibrils causes the cells to increase

in length more than width when turgor increases.

The two guard cells are attached at their tips, so the

increase in length causes buckling.

(a)

Figure 36.15aSlide67

Physiology Of the Guard Cell

Potassium ions are pumped into the vacuole

of the guard cell from surrounding cells

Higher concentration of K+ reduces the water potential causing an

influx of water

More water causes the

cell to swell

Uneven thickness of the cell wall causes the cell to curve and open

Loss of water causes the cell to become flaccid and closeSlide68

H

2

O

H

2

O

H

2

O

H

2

O

H

2

O

K

+

Role of potassium in stomatal opening and closing.

The transport of K

+

(potassium ions, symbolized

here as red dots) across the plasma membrane and

vacuolar membrane causes the turgor changes of

guard cells.

(b)

H

2

O

H

2

O

H

2

O

H

2

O

H

2

O

Figure 36.15bSlide69

Control of Guard Cells

Light

stimulation gives

energy for H+ pumps

Results in the co-transport of K+

CO

2

depletion in air space opens stomata

Circadian rhythm

: internal “

clock” – plants kept in the dark still open their stomata when it should be daySlide70

Stomatal

Modifications

Xerophytic

Plants (dry)

Lower epidermal

tissue

Trichomes

(“hairs”)

Cuticle

Upper epidermal tissue

Stomata

100



mSlide71

Cavitation

: Air bubble in the xylem – equivalent of an embolism in an artery – blocks the flow of water – plant reroutes through other xylemSlide72

Translocation of Phloem

Hydrostatic

Push

from

Source to Sink

Source:

Location of Sugar Production

Photosynthesis:

Leaves (summer and fall)Starch Metabolism:

Roots (spring)Sink: Location of Sugar Consumption or StorageFall (Roots)

Spring (buds for leaf and stem growth)Slide73

A chemiosmotic mechanism is responsible for

the active transport of sucrose into companion cells

and sieve-tube members. Proton pumps generate

an H

+

gradient, which drives sucrose accumulation

with the help of a cotransport protein that couples

sucrose transport to the diffusion of H

+

back into the cell.

(b)

High H

+

concentration

Cotransporter

Proton

pump

ATP

Key

Sucrose

Apoplast

Symplast

H

+

H

+

Low H

+

concentration

H

+

S

S

Figure 36.17b

Movement of Phloem Solution

Sugar is produced

Sugar is

cotransported

into the

cell with H+ ionsSlide74

Water potential in the cell is

lowered

Osmotic influx of water into the cell

Builds pressure inside of the cell and pushes the solution through the cells to the sink.

Vessel

(xylem)

H

2

O

H

2

O

Sieve tube

(phloem)

Source cell

(leaf)

Sucrose

H

2

O

Sink cell

(storage

root)

1

Sucrose

Loading of sugar (green

dots) into the sieve tube

at the source reduces

water potential inside the

sieve-tube members. This

causes the tube to take

up water by osmosis.

2

4

3

1

2

This uptake of water

generates a positive

pressure that forces

the sap to flow along

the tube.

The pressure is relieved

by the unloading of sugar

and the consequent loss

of water from the tube

at the sink.

3

4

In the case of leaf-to-root

translocation, xylem

recycles water from sink

to source.

Transpiration stream

Pressure flow