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Copyright © 2009 Pearson Education, Inc..
Lectures by
Gregory AhearnUniversity of North Florida
Chapter 43
Plant Anatomy and Nutrient
Transport
Copyright © 2009 Pearson Education Inc.
43.1 How Are Plant Bodies Organized?
Flowering plants have a root system and a shoot system.• Flowering plant bodies consist of two major
parts: the root system and the shoot system.• Roots are branched portions of the plant body
that are usually embedded in soil and serve to anchor the plant and absorb water and nutrients from the soil.
Copyright © 2009 Pearson Education Inc.
43.1 How Are Plant Bodies Organized?
Flowering plants have a root system and a shoot system (continued).• The part of the plant above ground is the
shoot system, and consists of leaves, buds, flowers, and fruit born on stems.
• The functions of shoots include photosynthesis, reproduction, and transport between different parts of the plant body.
Copyright © 2009 Pearson Education Inc.Fig. 43-1
root hairs
root cap
tap root
branch roots
terminal bud
flower
lateral bud
stem
leaf
branch
apical meristembeginningleaves
Sh
oot
syst
em
Root
syst
em
Copyright © 2009 Pearson Education Inc.
43.1 How Are Plant Bodies Organized?
Flowering plants can be divided into two groups:• The monocots, which include the grasses,
lilies, palms, and orchids• The dicots, which include deciduous trees
(those that drop their leaves in winter), bushes, and many garden flowers
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Flowers Leaves Roots SeedsStems
Flower parts are inthrees or multiplesof three
Flower parts are infours or fives or multiplesof four or five
Leaves have smoothedges, often narrow,with parallel veins
Leaves are palmate(handlike) or ovalwith netlike veins
Vascular bundlesare scatteredthroughout the stem
Monocots have afibrous root system
The seed has onecotyledon (seed leaf)
The seed hastwo cotyledons(seed leaves)
Dicots have ataproot system
Vascular bundlesare arranged in aring around the stem
Monoco
tsD
icots
embryo
cotyledon
embryo
cotyledons
43.1 How Are Plant Bodies Organized?
Fig. 43-2
Copyright © 2009 Pearson Education Inc.
43.2 How Do Plants Grow?
During growth, meristem cells give rise to differentiated cells.• Plant bodies are composites of two
fundamentally different kinds of cells: meristem and differentiated cells.
• Meristem cells are capable of mitosis.• Some meristem cells stop dividing and
become permanent, non-mitotic differentiated cells.
• Differentiated cells become mature leaves or trunks of trees.
Copyright © 2009 Pearson Education Inc.
43.2 How Do Plants Grow?
During growth, meristem cells give rise to differentiated cells (continued).• Plants grow by cell division of two types of
meristem cells:• Apical meristem, at tips of roots and shoots• Lateral meristem, also called cambia, form
cylinders that run lengthwise inside roots and stems
Copyright © 2009 Pearson Education Inc.
43.2 How Do Plants Grow?
Different processes are responsible for growth in length and width.• Primary growth occurs by division of apical
meristem cells, and leads to growth in length at the tips of roots and shoots.
• Secondary growth occurs by mitotic division of lateral meristem cells, and increases the thickness of the stems and roots as they age.
Copyright © 2009 Pearson Education Inc.
43.3 What Are The Tissues And Cell Types Of Plants? The structures of plants consist of three
types of plant tissues:• Dermal tissue, which covers the outer
surfaces of the plant body• Ground, nondermal, nonvascular tissue that
makes up most of the body of young plants• Vascular tissue, which transports water,
nutrients, and sugars throughout the plant
Copyright © 2009 Pearson Education Inc.
43.3 What Are The Tissues And Cell Types Of Plants? The structure of
the root and shoot
Fig. 43-3
vascular tissue vasculartissuesystem
groundtissuesystem
vasculartissuesystem
dermaltissuesystem
ground tissue
Shoot
syst
em
Root
syst
em
Copyright © 2009 Pearson Education Inc.
43.3 What Are The Tissues And Cell Types Of Plants? Dermal tissue covers the plant body.
• The outermost covering on leaves, stems, and roots of all young plants is part of the dermis called the epidermis.
• This part of the plant is covered by a waterproof layer known as a cuticle, which reduces evaporation of water from the plant.
• Roots have no cuticle because it would prevent the absorption of water and nutrients from the soil.
• Epidermal cells are replaced by cork cells as the plant ages.
Copyright © 2009 Pearson Education Inc.
leaf hair
stomata
43.3 What Are The Tissues And Cell Types Of Plants? Dermal tissues cover plant surfaces.
Fig. 43-4
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43.3 What Are The Tissues And Cell Types Of Plants? Ground tissue makes up most of the young
plant body.• Ground tissue cells typically carry out most of
the metabolic activities of the plant.• These tissues may photosynthesize, store
sugars and starches, or secrete hormones.• Roots of plants, like carrots and sweet
potatoes, are packed with ground tissue that stores carbohydrates such as starch and sugar.
• Ground tissue also provides support in stems such as celery stalks.
Copyright © 2009 Pearson Education Inc.
43.3 What Are The Tissues And Cell Types Of Plants? Vascular tissue consists of xylem and
phloem.• Vascular tissue occurs in strands, called
vascular bundles, that contain both xylem and phloem.
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43.3 What Are The Tissues And Cell Types Of Plants? Xylem conducts water and dissolved
nutrients from the roots to the rest of the plant.• Xylem tissues are called tracheids and vessel
elements.• Tracheids are thin in diameter, while the
vessel elements are wider and provide a relatively unobstructed pipeline from root to leaf.
Copyright © 2009 Pearson Education Inc.
43.3 What Are The Tissues And Cell Types Of Plants? Xylem
Fig. 43-5
tracheids
tracheids
ground tissuecells (fibers)
vesselelement
pits
endwall
vesselelement
Openings connectthe vessel elements
Pits link the insidesof the tracheids andvessel elements
(a) Xylem structure (b) Longitudinal section of xylem
Copyright © 2009 Pearson Education Inc.
43.3 What Are The Tissues And Cell Types Of Plants? Phloem conducts substances throughout
the plant.• Substances that are synthesized by the plant
—such as sugars, amino acids, and hormones—are conducted through the plant by phloem.
• Phloem has sieve tubes that form continuous conducting tubes that connect all parts of the plant.
Copyright © 2009 Pearson Education Inc.
groundtissuecells
Sieve plates connectthe sieve-tube elements
companioncell
sieve-tubeelement
nucleus companioncell
sieve platewith pores
(a) Phloem structure (b) Cross section of phloem
43.3 What Are The Tissues And Cell Types Of Plants? Phloem
Fig. 43-6
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43.4 How Do Roots Grow And What Do They Do? Dicots and monocots have different types of
roots.• Dicots, such as carrots and dandelions, have
a single taproot with smaller side roots.• Monocots, like grasses and palms, have
numerous roots at the base of the plant that are the same size, called fibrous roots.
Copyright © 2009 Pearson Education Inc.
43.4 How Do Roots Grow And What Do They Do? Taproots and fibrous roots
Fig. 43-7
Copyright © 2009 Pearson Education Inc.
43.4 How Do Roots Grow And What Do They Do? Roots elongate by primary growth.
• In young roots, divisions of the apical meristem give rise to four distinct regions:• An outer envelop of epidermis• A vascular cylinder at the core of the root• A cortex between the two• A protective root cap at the tip of the root
that protects the apical meristem from being scraped off as the root pushes downward
Copyright © 2009 Pearson Education Inc.
43.4 How Do Roots Grow And What Do They Do?
Fig. 43-8
root hairepidermis
cortex
endodermisof cortex
xylem
phloem
apicalmeristem
vascularcylinder
rootcap
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43.4 How Do Roots Grow And What Do They Do? The epidermis of the root is very permeable
to water.• The root’s outermost covering of cells is the
epidermis, which contacts the soil and any air or water trapped among the soil particles.
• The cell walls of epidermal cells are highly water permeable, allowing water to penetrate into the interior of the root.
Copyright © 2009 Pearson Education Inc.
43.4 How Do Roots Grow And What Do They Do? Many epidermal cells have root hairs, which
are long, thin extensions that grow into the surrounding soil and increase the roots ability to absorb water and nutrients.
Fig. 43-9
roothairs
Copyright © 2009 Pearson Education Inc.
43.4 How Do Roots Grow And What Do They Do? The cortex controls the absorption of water
and nutrients.• Cortex is a type of ground tissue that makes
up most of the inside of a young root.• The cortex consists of an outer mass of large,
loosely packed cells just beneath the epidermis, and an inner layer of smaller, close-fitting cells called the endodermis, which encircles the vascular cylinder.
Copyright © 2009 Pearson Education Inc.
43.4 How Do Roots Grow And What Do They Do? The cortex controls the absorption of water
and nutrients (continued).• Water and nutrients move from the cortex into
the vascular cylinder by moving across the membranes of the endodermal cells, which regulate the types and amounts of materials that the roots absorb.
Copyright © 2009 Pearson Education Inc.
43.4 How Do Roots Grow And What Do They Do? The vascular cylinder contains xylem and
phloem, and meristem for branch roots.• The vascular cylinder of a root contains the
conducting tissues of xylem and phloem, which transport water and dissolved materials within the plant.
• The outermost layer of the vascular cylinder retains the ability to divide and form the apical meristem of new roots that grow as branches from existing roots.
Copyright © 2009 Pearson Education Inc.
43.4 How Do Roots Grow And What Do They Do? A new branch root breaks out through the
cortex and epidermis of the primary root by secreting enzymes that digest them away.
The vascular tissues of the branch root connect with the vascular tissues of the primary root.
Fig. 43-10
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? Stems grow in length by the mitotic apical
stem cells of the terminal bud.• The apical meristem differentiates into four
specialized cell types: stem cells, bud cells, leaf cells, and flower cells.
• Young stems are composed of four tissues:• Epidermis (dermal tissue)• Cortex (ground tissue)• Pith (ground tissue)• Vascular tissue
Copyright © 2009 Pearson Education Inc.Fig. 43-11
terminal bud
apicalmeristem
beginning leaves
node
lateral bud
internode
branch(sproutedlateral bud)
stalk
bladeleaf
epidermis
cortex
phloem
vascularcambium xylem
pith
stemvascularbundle
pith
xylem
phloem vascularcambium
vascular bundle
sunflower(dicot)stem
epidermis cortexvascularbundle
pith
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? The epidermis of the stem retards water
loss while allowing carbon dioxide to enter.• The epidermis is perforated with adjustable
pores called stomata (singular, stoma) that permit and regulate the movement of carbon dioxide and oxygen.
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? The cortex and pith support the stem, store
food, and photosynthesize.• There are two types of ground tissue in stems:
• Cortex• Pith
• These ground tissues perform three major functions—support, storage, and photosynthesis.
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? Vascular tissues in stems transport water,
dissolved nutrients, and hormones.• Xylem and phloem of stems transport water,
nutrients, sugars, and hormones.• Vascular tissues are continuous in the root,
stem, and leaf, interconnecting all parts of the plant.
• Xylem and phloem in young stems arise from the apical meristem, and are called primary xylem and primary phloem.
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? Branches form from lateral buds consisting
of meristem cells.• As the shoot grows, small clusters of
meristem cells are left behind on the surface of the stem.
• Some of these meristem cells form leaves, and others form lateral buds that grow into branches.
• Lateral buds are located just above the attachment points of leaves.
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? A bud sprouts from
these meristem cells when stimulated by a hormone, and this becomes a branch that has its own apical meristem and makes its own leaves.
Fig. 43-12
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43.5 How Do Stems Grow And What Do They Do? Secondary growth produces thicker,
stronger stems.• Secondary growth results from cell division in
two lateral meristems:• The vascular meristem• The cork cambium
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43.5 How Do Stems Grow And What Do They Do? Vascular cambium produces secondary
xylem and phloem.• The vascular cambium is a cylinder of
meristem cells located between the primary xylem and the primary phloem.
• Daughter cells of the vascular cambium produced toward the inside of the stem differentiate into secondary xylem, and those produced toward the outside of the stem differentiate into secondary phloem.
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? Vascular cambium produces secondary
xylem and phloem (continued).• Since the center of the stem already is filled
with pith and primary xylem, newly formed secondary xylem pushes the vascular cambium farther out, increasing the diameter of the stem.
Copyright © 2009 Pearson Education Inc.Fig. 43-13
primary xylem
primary phloem
dividingvascularcambium
dividingvascularcambium
newsecondaryxylem
newsecondaryphloem
primaryxylem
primaryphloem
cortex
End of primarygrowth
Secondary growth
secondary phloemprimary phloemvascular cambium
primary xylem
secondary xylemepidermiscork cambiumcork
cortexpith
pith
(a) Cross section of stem
(b) Detail of vascular bundle
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43.5 How Do Stems Grow And What Do They Do? Tree rings reflect seasonal changes.
• Tree rings form from seasonal changes in vascular cambium growth.
• In temperate climates, vascular cambium growth ceases in the winter but starts to grow in the spring, forming new xylem and phloem.
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? Tree rings reflect seasonal changes (continued).• In spring months, the new cells are large due
to extensive water uptake, but in summer months, when water is more scarce, the cells are smaller.
• As a result, cross-sections of tree trunks show a banding pattern of these different cells that form annual growth rings, which can be used to age the tree.
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? Secondary growth causes the epidermis to
be replaced by woody cork.• Epidermal cells are mature, differentiated cells
that can no longer divide.• Therefore, as new secondary xylem and
phloem enlarge the stem, the epidermis splits and dies.
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? Secondary growth causes the epidermis to
be replaced by woody cork (continued).• Then some cells of the cortex form a new
lateral meristem—the cork cambium—which produces daughter cells toward the outside of the stem.
• These daughter cells become cork cells that protect the tree from damage as they become part of the tree bark.
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do?
PLAYPLAY Animation—Primary and Secondary Growth
Copyright © 2009 Pearson Education Inc.
43.5 How Do Stems Grow And What Do They Do? Some specialized stems produce new
plants or store water or food.• Many plants have stems that are modified to
perform functions very different from the original one of raising leaves up to the light.
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43.5 How Do Stems Grow And What Do They Do? Strawberries grow stems that snake out
over the soil, sprouting new strawberry plants where lateral buds touch the soil.
Fig. 43-14a
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43.5 How Do Stems Grow And What Do They Do? The Baobab tree
stores water in aboveground stems; other plants, such as the potato, store carbohydrates in underground stems.
Fig. 43-14b
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43.6 What Is The Structure Of Leaves And What Do They Do? Leaves are the major site of photosynthesis
in plants. Photosynthesis produces sugars (glucose)
and oxygen from water, CO2, and sunlight.
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43.6 What Is The Structure Of Leaves And What Do They Do? Leaves have two major parts:
• The leaf epidermis consists of a layer of nonphotosynthetic, transparent cells that secrete a cuticle that reduces evaporation; adjustable pores called stomata surrounded by guard cells occur throughout the epidermis and regulate gas exchange.
• Beneath the epidermis is the mesophyll, which contains the chloroplasts for photosynthesis.
Copyright © 2009 Pearson Education Inc.
43.6 What Is The Structure Of Leaves And What Do They Do? A typical dicot leaf
Fig. 43-15
upperepidermis
mesophyll
lowerepidermis
stomaguard cell
chloroplasts
stoma phloem xylemxylem phloemcuticle
cuticle upperepidermis
(a) Leaf structure (b) Leaf cross section
lowerepidermis
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43.6 What Is The Structure Of Leaves And What Do They Do? Specialized leaves may provide support,
store food, or even capture insects.• In some plants, modified leaves serve
functions unrelated to photosynthesis or water conservation.
• The common edible pea grasps fences with clinging tendrils, which are slender, supple leaflets.
• Some plants—like onions, daffodils, and tulips—use thick, fleshy leaves as food-storage organs.
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43.6 What Is The Structure Of Leaves And What Do They Do? A few plants have become predators;
sundews have leaves that are modified into snares for trapping insects.
Fig. 43-16
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43.7 How Do Plants Acquire Nutrients?
Plants require a long list of important nutrients for normal life, which come from the soil or air.• Carbon dioxide• Hydrogen and oxygen• Phosphorus• Nitrogen • Minerals such as magnesium, calcium, and
potassium• Micronutrients such as iron, copper,
manganese, zinc, boron, and molybdenum
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43.7 How Do Plants Acquire Nutrients?
Fungi and bacteria help plants acquire nutrients.• Root-fungus
complexes are called mycorrhizae, and they help plants extract and absorb minerals from the soil.
Fig. 43-43
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43.7 How Do Plants Acquire Nutrients?
Plants need a lot of nitrogen; much comes from the air, but some plants have symbiotic bacteria in root nodules that convert N2 gas into ammonium or nitrate, which the plants can then use.
This process is called nitrogen-fixation.• Plants that have nitrogen-fixing bacteria are
called legumes (e.g., peas, clover, and soybeans).
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43.7 How Do Plants Acquire Nutrients?
Nitrogen fixation in legumes
Fig. 43-18
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43.8 How Do Plants Acquire Water And Transport Water And Nutrients? Nearly 99% of the water absorbed by the
roots of plants evaporates through the stomata of leaves in a process called transpiration.• Transpiration drives the movement of water
through the plant body by pulling water up through the xylem of the roots and stem into the leaves.
Copyright © 2009 Pearson Education Inc.
43.8 How Do Plants Acquire Water And Transport Water And Nutrients? Transpiration provides the force for water
movement in xylem.• As the leaf transpires, the water concentration
in its mesophyll drops, which causes water to move by osmosis from the leaf’s xylem into the mesophyll cells.
• Because of hydrogen bonding between adjacent water molecules, when one water molecule leaves, it pulls other water molecules up the xylem from the stem and the roots.
Copyright © 2009 Pearson Education Inc.Fig. 43-19
Water evaporatesthrough the stomataof leaves
water molecules
Cohesion of watermolecules to oneanother and adhesionto the xylem wall byhydrogen bondscreates a “water chain”
Water entersthe vascularcylinder of the root
flo
w o
f w
ater
Copyright © 2009 Pearson Education Inc.
43.8 How Do Plants Acquire Water And Transport Water And Nutrients? Water enters roots mainly by pressure
differences created by transpiration.• The upward movement of water ultimately
causes soil water to move into the roots.• The main force powering the flow of water
from the soil to the root’s vascular cylinder is low water pressure in the cylinder.
Copyright © 2009 Pearson Education Inc.
43.8 How Do Plants Acquire Water And Transport Water And Nutrients? Water enters roots mainly by pressure
differences created by transpiration (continued).• This low pressure is due to the fact that water
is always drawn away by moving upward through the xylem to replace water lost through transpiration from the leaves.
• This force is strong enough that roots can absorb water, even from quite dry soils.
Copyright © 2009 Pearson Education Inc.
43.8 How Do Plants Acquire Water And Transport Water And Nutrients? Adjustable stomata control the rate of
transpiration.• Transpiration is a plant’s largest source of
water loss.• Most water is lost through the stomata in the
leaves; because photosynthesis requires carbon dioxide from the air, the stomata have to be open to obtain this gas.
• To meet these requirements, stomata are open during the day, when sunlight allows photosynthesis, and closed at night, conserving water.
Copyright © 2009 Pearson Education Inc.
43.8 How Do Plants Acquire Water And Transport Water And Nutrients?
PLAYPLAY Animation—Plant Transport Mechanisms
Copyright © 2009 Pearson Education Inc.
Water Transport In Plants
Suggested Media Enhancement:
Water Transport in PlantsTo access this animation go to folder C_Animations_and_Video_Filesand open the BioFlix folder.
Copyright © 2009 Pearson Education Inc.
43.8 How Do Plants Acquire Water And Transport Water And Nutrients? The pressure-flow theory explains sugar
movement in phloem.• Sugars made by photosynthesis must be
moved to other parts of the plant.• Sugars, dissolved in water to form sap, also
contain amino acids and hormones, and travel throughout the phloem.
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43.8 How Do Plants Acquire Water And Transport Water And Nutrients? The pressure-flow theory explains sugar
movement in phloem (continued).• After reaching their destination, the sugars
may nourish non-photosynthetic cells of roots or flowers, or may be stored for later use.
• Sap is propelled through phloem by differences in water pressure created by the difference between the production and use of sugar in different parts of the plant.
Copyright © 2009 Pearson Education Inc.
43.8 How Do Plants Acquire Water And Transport Water And Nutrients? The pressure flow theory is illustrated in four
steps.1. The sugar produced by a source cell is moved by
active transport into a phloem tube.
2. Water follows the sugar into the tube by osmosis.
3. The increased water pressure forces the sugar-rich sap through the phloem tubes into regions of lower pressure.
4. Cells of a sugar sink actively transport sugar out of the phloem, with water following by osmosis.