Download Chapter 25

BIOLOGY
Chapter 25: pp. 455 - 472
10th Edition
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Leaf
xylem
phloem
intercellular
spaces
stoma
O2 CO2
O2
H2O
CO2
H2O
sugar
H2O
Stem
CO2
Sylvia S. Mader
Flowering Plants:
Nutrition and Transport
O2
H2O
xylem
H2O
phloem
sugar
Root
H2O
O2
xylem
phloem
H2O
CO2
minerals
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
1
Outline

Essential Inorganic Nutrients

Soil Formation

Soil Profiles

Soil Erosion

Water & Mineral Uptake

Transport Mechanisms

Water and Minerals

Organic Nutrients
2
Plant Nutrition and Soil

Essential Inorganic Nutrients



About 95% of a plant’s dry weight is carbon, hydrogen,
and oxygen
Primary nutrients are carbon dioxide and water
A nutrient is essential if



It has an identifiable role,
Another nutrient cannot substitute for it, and
A deficiency of the nutrient causes a plant to die

Macronutrients
 Micronutrients
3
Overview of Plant Nutrition
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
CO2
O2
H2O
O2
H2O
CO2
minerals
4
Nutrient Deficiencies
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. Solution lacks nitrogen
b. Solution lacks phosphorus
c. Solution lacks calcium
Complete nutrient solution
Complete nutrient solution
Complete nutrient solution
Courtesy Mary E. Doohan
5
Soil Formation

Soil formation begins with weathering of rock

Organisms also play an important role


Lichens and Mosses

Humus begins to accumulate
Under ideal conditions, a centimeter of soil
may develop within 15 years
6
Nutritional Function of Soil

Soil is a mixture of:







Mineral particles
Decaying organic material
Living organisms
Air, and
Water
Roots take up oxygen from air spaces
Soils are a mixture of three types of particles



Sand
Clay
Silt
7
Absorbing Minerals
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
negatively charged soil particle
K+
K+
K+
Ca2+
Ca2+
root hair
Ca2+
H+
K+
H+
Ca2+
K+
K+
Ca2+
film of water
air space
epidermis of root
8
Soil Profiles

A soil profile is a vertical section from
ground surface to unaltered rock below

Parallel layers - Horizons
A (topsoil) - Litter and humus
 B (subsoil) - Inorganic nutrients
 C (parent material) - Weathered rock


Because parent material and climate differ, the
soil profile varies according to the particular
ecosystem
9
Simplified Soil Profile
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Soil horizons
Topsoil: humus
plus living
organisms
A
Zone of leaching:
removal of nutrients
B
Subsoil:
accumulation
of minerals and
organic materials
Parent material:
weathered rock
C
10
Soil Erosion
Soil erosion occurs when water or wind
carry soil away to a new location
 Worldwide, erosion removes about 25
billion tons of topsoil annually

Deforestation
 Desertification
 Poor farming practice

11
Water and Mineral Uptake

Water and minerals enter the roots of flowering
plants through the same pathways


Between porous cell walls, then forced into
endodermal cells by the Casparian strip
Through root hairs, through cells across the cortex and
endodermis via cytoplasmic strands within
plasmodesmata

Water enters root cells when their osmotic
pressure is lower than that of the soil
 Minerals are actively taken up by plant cells and
are transported in the xylem along with water
12
Water and Mineral Uptake
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
endodermis
pericycle
phloem
xylem
cortex
50 mm
An ATP-driven
pump transports
H+ out of cell.
1
vascular cylinder
2
The electrochemical
gradient causes K+
to enter by way of a
channel protein.
pericycle
ATP
H+
ADP +
K+
P
K+
Endodermal Cell
H+
I-
I-
H+
I-
I-
K+
endodermis
and Casparian
strip
H+
I-
K+
K+
cortex
H+
Pathway A
of water and
minerals
a.
epidermis
H+
root hair
pathway B
of water and
minerals
H+
H+
I-
K+
3
Negatively charged ions
(I−) are transported
along with H+ into cell.
Water Outside Endodermal Cell
b.
a: © CABISCO/Phototake
13
Adaptations of Roots for
Mineral Uptake

Important Symbiotic Relationships

Rhizobium bacteria live in root nodules



Bacteria fix atmospheric nitrogen
Host plant provides the bacteria with carbohydrates
Mycorrhizal association between fungi and plant roots


Fungus increases the surface area for water and mineral
uptake and break down organic matter
Root provides the fungus with sugars and amino acids

Parasitic plants
 Carnivorous plants
14
Root Nodules
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
root
nodule
bacteria
Portion of infected cell
(Top): © Dwight Kuhn; (Circle): © E.H. Newcomb & S.R. Tardon/Biological Photo Service
15
Mycorrhizae
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Mycorrhizae present
Mycorrhizae not present
mycorrhizae
(Top): © B. Runk/S. Schoenberger/Grant Heilman Photography; (Circle): © Dana Richter/Visuals Unlimited
16
Other Ways to Acquire Nutrition
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
dodder
(brown)
bulbs release
digestive enzymes
a. Dodder, Cuscuta sp.
Sundew leaf
enfolds prey
sticky
hairs
narrow
leaf form
b. Cape sundew , Drosera capensis
a: © Kevin Schafer/Corbis; b(Plant): © Barry Rice/Visuals Unlimited; b(Leaf): © Dr. Jeremy Burgess/Photo Researchers, Inc.
17
Transport Mechanisms in Plants

Vascular tissues transport water and nutrients

Xylem transports water and minerals

Two types of conducting cells




Tracheids
Vessel Elements
Water flows passively from an area of higher water potential to
an area of lower water potential
Phloem transports organic materials

Conducting cells are sieve-tube members



Have companion cells to provide proteins
End walls are sieve plates
Plasmodesmata extend through sieve plates
18
Plant Transport System
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Leaf
xylem
intercellular
spaces
phloem
stoma
O2
H2O
CO2
O2
CO2
H2O
sugar
Stem
H2O
xylem
phloem
sugar
Root
H2O
H2O
xylem
phloem
19
The Concept of Water Potential
Potential energy is stored energy
 Water potential is the energy of water.



Water moves from a region of higher potential
to a region of lower potential
In terms of cells, two factors usually
determine water potential:
Water pressure across a membrane
 Solute concentration across a membrane

20
The Concept of Water Potential

Pressure potential is the effect that pressure has
on water potential.



Water moves across a membrane from the area of
higher pressure to the area of lower pressure.
The higher the water pressure, the higher the water
potential.
Osmotic potential takes into accounts the
presence of solutes


Water tends to move from the area of lower solute
concentration to the area of higher solute
concentration.
The lower the concentration of solutes (osmotic
potential), the higher the water potential.
21
Water Potential and Turgor Pressure
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
central vacuole
Wilted
central vacuole
cell wall
Turgid
cell wall
H2O
enters
the cell
higher
Extracellular fluid:
Equal water
potential inside and
outside the cell
water potential
pressure potential
osmotic potential
lower
Inside the cell:
Pressure potential
increases until
the cell is turgid
water potential
pressure potential
osmotic potential
a. Plant cells need water.
b. Plant cells are turgid.
(Both): © Dwight Kuhn
22
Water Transport

Xylem vessels form an open pipeline
The vessel elements are separated by
perforated plates
 Water moves into an out of tracheids through
pits


Water entering roots creates a positive
pressure (root pressure)

Pushes xylem sap upward
May be responsible for guttation
 Water forced out vein endings along edges of
leaves

23
Conducting Cells of Xylem
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
pits
20 mm
20 mm
a. Perforation plate with a single, large opening b. Perforation plate with a series of openings
50 mm
c. Tracheids
a, b: Courtesy Wilfred A. Cote, from H.A. Core, W.A. Cote, and A.C. Day, Wood: Structure and Identification 2/e; c: Courtesy
W.A. Cote, Jr., N.C. Brown Center for Ultrastructure Studies, SUNY-ESF
24
Guttation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Ed Reschke/Peter Arnold, Inc.
25
Cohesion-Tension Model

Cohesion-tension model of xylem transport
suggests a passive xylem transport
Cohesion is the tendency of water molecules
to cling together
 Adhesion is the ability of the polar water
molecules to interact with molecules of vessel
walls
 A continuous water column moves passively
upward due to transpiration

26
Cohesion-Tension Model

Leaves





Stem


Transpiration causes water loss through stomata
Water molecules that evaporate are replaced by water molecules
from leaf veins
Due to cohesion, transpiration exerts a pulling force (tension)
drawing water through the xylem to the leaf cells
Waxy cuticle prevents water loss when stomata are closed
Tension in xylem pulls the water column upward
Roots

Water enters xylem passively by osmosis and is pulled upward
due to tension in xylem
27
Cohesion-Tension Model of Xylem
Transport
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
mesophyll
cells
xylem in
leaf vein
Leaves
• Transpiration
creates tension.
stoma
• Tension pulls the water
column upward from
the roots to the leaves.
H2O
intercellular
space
cohesion by hydrogen bonding
between water molecules
adhesion due to
polarity of water
molecules
H2O
cell wall
water molecule
Stem
• Cohesion makes
water continuous.
• Adhesion keeps water
column in place.
xylem
H2O
water molecule
root hair
H2O
Roots
• Water enters xylem at
root.
• Water column extends
from leaves to the root.
xylem
28
Opening and Closing of Stomata

Each stoma in leaf epidermis is bordered
by guard cells
Increased turgor pressure in guard cells opens
stoma
 Active transport of K+ into guard cells causes
water to enter by osmosis and stomata to open
 Opening and closing of stomata is regulated by
light

29
Opening and Closing of Stomata
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Open stoma
H2O
H2O
Vacuole
K+
stoma
25 m
a.
25 mm
K+ enters guard cells, and water follows.
Closedstoma
H2O
H2O
K+
b.
25 mm
K+ exits guard cells, and water follows.
30
Organic Nutrient Transport

Role of Phloem
Phloem transports sugar
 Girdling of tree below the level of leaves
causes bark to swell just above the cut



Sugar accumulates in the swollen tissue
Radioactive tracer studies confirm that phloem
transports organic nutrients

Phloem sap can be collected using aphids
31
Acquiring Phloem Sap
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. An aphid feeding on a plant stem
b. Aphid stylet in place
a: © M.H. Zimmermann, Courtesy Dr. P.B. Tomlinson, Harvard University; b: © Steven P. Lynch
32
Pressure-Flow Model of
Phloem Transport

Sieve tubes form a continuous pathway for
organic nutrient transport



Sieve-tube members are aligned end to end
Strands of plasmodesmata extend through sieve plates
between sieve-tube members
Positive pressure drives the movement of sap in
sieve tubes



Sucrose is actively transported into phloem at the
leaves
Water follows by osmosis, creating positive pressure
The increase in pressure causes flow that moves water
and sucrose to a sink
33
Pressure-flow Model of
Phloem Transport
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
mesophyll cell of leaf
Leaf
phloem
xylem
sugar
water
xylem
phloem
cortex cell
of root
xylem
phloem
Root
34
Review

Essential Inorganic Nutrients

Soil Formation

Soil Profiles

Soil Erosion

Water & Mineral Uptake

Transport Mechanisms

Water and Minerals

Organic Nutrients
35
Chapter 25: pp. 455 - 472
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
10th Edition
Sylvia S. Mader
Flowering Plants:
Nutrition and Transport
BIOLOGY
36