ch 43 lecture

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.



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



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


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


Fig. 43-2


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.



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



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.


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


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


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.


leaf hair

stomata

43.3 What Are The Tissues And Cell Types Of Plants? Dermal tissues cover plant surfaces.

Fig. 43-4


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.


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.


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.


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


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.


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


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.


43.4 How Do Roots Grow And What Do They Do? Taproots and fibrous roots

Fig. 43-7


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


43.4 How Do Roots Grow And What Do They Do?

Fig. 43-8

root hairepidermis

cortex

endodermisof cortex

xylem

phloem

apicalmeristem

vascularcylinder

rootcap


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.


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


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.


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.


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.


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


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


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


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.


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.


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.


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.


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


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


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.


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.


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


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.


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.


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.


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.


43.5 How Do Stems Grow And What Do They Do?

PLAYPLAY Animation—Primary and Secondary Growth


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.


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


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


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.


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.


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


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.


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


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



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



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).



Nitrogen fixation in legumes

Fig. 43-18


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.


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.


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


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.


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.


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.


43.8 How Do Plants Acquire Water And Transport Water And Nutrients?

PLAYPLAY Animation—Plant Transport Mechanisms


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.


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.


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.


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.


xylem phloem

sugarsink

sugarsource

sugarsourcecell

sugarsink cell

sunlight

43.8 How Do Plants Acquire Water And Transport Water And Nutrients? Pressure differences power the movement

of sugars.

Fig. 43-20

ch 43 lecture

Education

pearson education

types of meristem cells

flowering plant bodies

shoot system

plant body

plant anatomy

fibrous root system

different kinds of cells