Chapter 25: pp. 455 - 472
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 intercellular spaces stoma xylem phloem
O
2
H
CO
2
2
O
O
2 CO
2
H
2
O
H
2
O sugar
Stem
CO
2
O
2
H
2
O xylem phloem
H
2
O sugar
Root
H
2
O
O
2
CO
2
H
2
O minerals xylem phloem
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
BIOLOGY
10th Edition
1

 Essential Inorganic Nutrients
 Soil Formation
 Soil Profiles
 Soil Erosion
 Water & Mineral Uptake
 Transport Mechanisms
 Water and Minerals
 Organic Nutrients
2

 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
CO
2
O
2
H
2
O
O
2
CO
2 minerals
H
2
O
4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. Solution lacks nitrogen Complete nutrient solution b. Solution lacks phosphorus Complete nutrient solution c. Solution lacks calcium Complete nutrient solution
Courtesy Mary E. Doohan
5

 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

 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
negatively charged soil particle
K +
K +
Ca 2+
K +
Ca 2+ root hair
Ca 2+
H +
K +
H +
Ca 2+
K +
Ca 2+ air space
K + film of water epidermis of root
8

 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Soil horizons
Topsoil: humus plus living organisms
Zone of leaching: removal of nutrients
Subsoil: accumulation of minerals and organic materials
A
B
Parent material: weathered rock
C
10

 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 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

50 m m vascular cylinder pericycle endodermis and Casparian strip cortex
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
endodermis pericycle phloem xylem cortex
1
ATP
An ATP-driven pump transports
H + out of cell.
2
The electrochemical gradient causes K + to enter by way of a channel protein.
K +
K +
H +
ADP + P
K +
K +
K +
H +
Endodermal Cell
I -
I -
H +
I -
I -
H +
I a.
Pathway A of water and minerals epidermis root hair
H +
H +
H + pathway B of water and minerals
Water Outside Endodermal Cell b.
a: © CABISCO/Phototake
K +
3
H + I -
Negatively charged ions
(I
−
) are transported along with H + into cell.
13

 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

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

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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
dodder
(brown) bulbs release digestive enzymes a. Dodder, Cuscuta sp.
sticky hairs narrow leaf form
Sundew leaf enfolds prey b. Cape sundew , Drosera capensis a: © Kevin Schafer/Corbis; b(Plant): © Barry Rice/Visuals Unlimited; b(Leaf): © Dr. Jeremy Burgess/Photo Researchers, Inc.
17

 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Leaf intercellular spaces stoma
O
2
H
2
O
CO
2
O
2
H
2
O
CO
2 xylem phloem
H
2
O sugar
Stem xylem phloem
H
2
O sugar
Root
H
2
O xylem phloem
19

 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

 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

cell wall central vacuole
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Wilted cell wall central vacuole
Turgid
Extracellular fluid: water potential pressure potential osmotic potential
Inside the cell: water potential pressure potential osmotic potential a. Plant cells need water.
H
2
O enters the cell
Equal water potential inside and outside the cell
Pressure potential increases until the cell is turgid b. Plant cells are turgid.
(Both): © Dwight Kuhn
22

 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

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 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
50 mm
24

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Ed Reschke/Peter Arnold, Inc.
25

 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




Leaves




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
Stem
 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
xylem in leaf vein
Leaves
• Transpiration creates tension.
• Tension pulls the water column upward from the roots to the leaves.
H
2
O cohesion by hydrogen bonding between water molecules adhesion due to polarity of water molecules
H
2
O cell wall stoma intercellular space mesophyll cells water molecule
Stem
• Cohesion makes water continuous.
• Adhesion keeps water column in place.
water molecule xylem
H
2
O root hair
H
2
O
Roots
• Water enters xylem at root.
• Water column extends from leaves to the root.
xylem
28

 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Open stoma
H
2
O H
2
O
Vacuole stoma
K + a.
25 m m
K + enters guard cells, and water follows.
Closedstoma
H
2
O H
2
O
25 m m
K + exits guard cells, and water follows.
K + b.
30

 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

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

 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

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
mesophyll cell of leaf xylem sugar water phloem
Leaf phloem xylem cortex cell of root xylem phloem
Root
34

 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
BIOLOGY
10th Edition
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display
36