1 Chapter 24 Flowering Plants: Structure and Function Professor Nearing, Macomb Community College

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Chapter 24 Flowering Plants: Structure and

Function

Professor Nearing, Macomb Community College

Objectives

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Define: vascular tissue, stomata, guard cells, meristem, cuticle, palisade layer, spongy layer, epidermis

Distinguish monocots from eudicots.List and describe the functions of the tissues in the

root, stem, and leaf.State and describe the two types of vascular tissue

according to general location and direction of fluid transport.

Explain how the meristem is related to plant growth.Explain how the structures of a leaf, stem, and root are

related to their functions.Briefly describe the transport of water and sugars

within a vascular plant. (Chapter 25, Sections 2 and 3)

Overview of Plants

All plants are multicellular & contain chlorophyll inside of chloroplasts

Plants (also called autotrophs or producers) trap energy from the sun by photosynthesis & store it in organic compounds

Heterotrophs or consumers get their energy directly or indirectly from plants

Plants also release oxygen needed by consumers

All plants are multicellular, eukaryotic organisms that reproduce sexually

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Overview of Plants continuedMany medicines are produced by plants Plants are very diverse & may be terrestrial or

aquatic Vary in size from 1 mm in width to more than

328 feet May live a few weeks or some over 5000 years Kingdom Plantae is divided into 12 phyla or

Divisions More than 270,000 plant species identified,

but new species still unidentified in tropical rain forests

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Classification of PlantsSome plants are non-vascular (=bryophytes)

Nonvascular plants lack vascular tissue and do not have true roots, stems, or leaves (mosses, liverworts, & hornworts)

Vascular plants, true roots, stems, & leaves, but may or may not produce seeds

Some plants are seedless, vascular plants (e.g., ferns)Most plants are seed-bearing, vascular plant

gymnosperms (no flowers, e.g., conifers)angiosperms (all produce flowers: dicots and monocots)monocots reproduce by "double fertilization“ their leaves

have parallel veins, and they have vascular bundles distributed throughout the ground tissue of the stem (palms, lilies, orchids and grasses -- including major food crops)

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Plant Structures and FunctionsVascular tissue: specialized tissue for

carrying food , water, & minerals.Two types of vascular tissue

xylem : carries water & inorganic nutrients from the roots to the stem & leaves

phloem : carries carbohydrates made by the plants to wherever they're needed or stored in the plant

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Plant Structures and Functions: Xylem and PhloemSome plants formed woody tissue from xylem

for extra support, while others kept a flexible, non-woody stem (herbaceous plants)

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Plant Structures and Functions continuedA waxy covering or cuticle developed on all plant parts

exposed to air which slowed transpiration (water loss) Openings in the cuticle called stomata allowed movement of

gases Two guard cells on each side of a stoma helped open & close

the opening When guard cells lose water & shrink, the stoma closes (prevents water

loss in the hotter times of the day) When guard cells swell with water, the stoma opens for gas exchange

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Plant Structures and Functions continued: StomataTranspiration is the evaporation of water from

plants. It occurs chiefly at the leaves while their stomata are open for the passage of CO2 and O2 during photosynthesis.

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Structure of Flowering Plants: Roots

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Generally, the root system is at least equivalent in size and extent to the shoot systemAnchors plant in soil

Absorbs water and minerals

Produces hormones

Store food produced by photosynthesis in plant parts above

Structure of Flowering Plants: Roots

Structurescells in apical meristem divide, then differentiate into

root epidermis, ground tissues and vascular tissues

vascular tissues form a vascular cylinder arranged as a central column surrounded by cortex; endodermis = innermost layer of cortex surrounds vascular cylinder and helps control water movement into it

pericycle lies just inside endodermis; = meristematic tissue that can give rise to lateral roots

Root hairs:Projections from epidermal root hair cells

Greatly increase absorptive capacity of root

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Root Diversity

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Primary root (taproot) - Fleshy, long single root, that grows straight down

Stores food

Fibrous root system - Slender roots and lateral branches

Anchors plant to soil

Adventitous roots - Roots develop from organs of the shoot system

Prop roots

Root Diversity

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Haustoria:Rootlike projections that grow into host plantMake contact with vascular tissue and

extract water and nutrientsMycorrhizas:

Associations between roots and fungiAssist in water and mineral extraction

Root nodules - Contain nitrogen-fixing bacteria

Root Diversity

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Structure of Flowering Plants: Stems

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Shoot system of a plant is composed of the stem, branches, and leavesStem is the main axis of a plant that elongates and

produces leavesStem also has vascular tissue that transports water

and mineralsshoots = above ground parts -- stems provide support

for leaves (photosynth.), flowers, fruitsroots = parts under the ground -- absorb water and

dissolved nutrientsThree tissue system

ground tissue -- bulk of plant bodyvascular tissue -- distribution of water and solutesdermal tissue -- covering, protection of plant surface

Stem Diversity

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Stolons:Above-ground horizontal stemsProduce new plants when nodes touch the

groundRhizomes:

Underground horizontal stemsContribute to asexual reproductionVariations:

Tubers - Enlarged portions functioning in food storageCorms - Underground stems that produce new plants

during the next season

Stem Diversity

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rhizome

branch

axillarybud

axillarybud

adventitious roots

adventitious roots

adventitiousroots

paperyleaves

a. Stolon b. Rhizome c. Tuber d. Corm

stolon

tuber

corm

rhizome

node

a: © Stanley Schoenberger/Grant Heilman Photography; b: © William E. Ferguson; 19c, d: © The McGraw Hill Companies, Inc./Carlyn Iverson, photographer

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Structure of Flowering Plants: Leaves

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Leaves are the major part of the plant that carries on photosynthesisFoliage leaves are usually broad and thin

Blade - Wide portion of foliage leafPetiole - Stalk attaches blade to stemLeaf Axil - Axillary bud originates

Tendrils - Leaves that attach to objectsBulbs - Leaves that store food

Structure of Flowering Plants: LeavesLayers (top to bottom)

cuticle upper epidermis palisade mesophyll spongy mesophyll lower epidermis (contains stomata) cuticle

Leaf structure/functionphotosynthesis in parenchyma cells in mesophyllvein : vascular bundles for movement of water,

solutes, products of photosynthesis.air spaces for gas exchangestomata (mostly on lower epidermis) to regulate water loss

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Structure of Flowering Plants: LeavesOrigin of leaves

leaves develop on the flanks of the tips of stems as outgrowths of apical meristems

buds are meristem tissues covered by modified leaves; terminal buds occur at the tips of shoots; lateral buds form in the upper angles where the leaf petiole is attached to the stem.

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Leaf Structure

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O2 and H2Oexit leafthrough stoma.

guard cell

cuticle

stoma

lower epidermis

spongymesophyll

leaf vein

air space

upper epidermis

cuticle

trichomes

100 m

nucleus

chloroplast

mitochondrion

central vacuole

Leaf cell Stoma and guard cells

SEM of leaf cross section

epidermal cell

bundle sheath cell

nucleus

stoma

chloroplast

leaf vein

palisademesophyll

Water and mineralsenter leaf through xylem.

Sugar exits leafthrough phloem.

CO2 enters leafthrough stoma.

lowerepidermis

spongymesophyll

palisademesophyll

upperepidermis

© Jeremy Burgess/SPL/Photo Researchers, Inc.

Leaf Diversity

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a: © Patti Murray Animals Animals/Earth Scenes; b: © Gerald & Buff Corsi/Visuals Unlimited; c: © P. Goetgheluck/Peter Arnold, Inc.

a. Cactus, Opuntia b. Cucumber, Cucumis c. Venuss flytrap, Dionaea’

spinestem tendril

hingedleaves

Classification of Leaves

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Simple leaf, magnolia

Pinnately compound leafblack walnut,

Palmately compound leaf,buckeye

Alternate leaves,beech

Opposite leaves, maple

Whorled leaves,bedstraw

a. Simple versus compound leaves b. Arrangement of leaves on stem

axillary bud

axillary buds


Structure of Flowering PlantsMeristems local regions of embryonic (undifferentiated)

cellsapical meristems -- tips of stems and root where growth

results in increase in length of stems and roots; produced by cell division and enlargement

lateral meristems -- growth produces thickening of stems and roots; vascular cambium produces vascular tissues, cork cambium produces cork

meristem cells can divide; mature, differentiated cells are specialize in structure and function and usually do not divide.

Continued divisions of meristem cells keeps a plant growing throughout it's life = indeterminate growth. Differentiated daughter cells form relatively permanent parts of the plant.

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Structure of Flowering PlantsPrimary growth as a stem (or root) grows

longer, primary meristems develop behind the growing tip these develop into the three tissue systems:protoderm -epidermis (waxy covering in

shoots)procambium-vascular cambium

--> primary xylem and phloemground meristem -->ground tissues--> cork cambium

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Structure of Flowering Plants: Angiosperms

Flowering plants whose seeds are produced & protected within the fruit

Flowering plants are the most successful group of plants today

They live in almost all possible habitats All flowering plants produce both flowers &

fruit

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Structure of Flowering Plants:

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stem

internode

leaf

petiole

blade

axillary bud

terminal bud

node

vascular tissues

root hairs

primaryroot

branchroot

shoot systemroot system

node

vein


Vegetative Organs of Several Eudicots

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(All): © Dwight Kuhn

stem

stems

petiole

lateral root

roots

blade

a. Root system, dandelion b. Shoot system, bean seedling c. Leaves, pumpkin seedling


Monocots vs. Dicots• Monocots include grasses, lilies, irises,

palms; dicots include common trees and shrubs (other than conifers = gymnosperms)

• Monocot seeds have one cotyledon (seed leaf); dicot seeds have two.

• Monocots have vascular bundles distributed throughout ground tissue of stem; dicots have bundles of vascular tissue positioned in a ring in stem. Xylem faces center; vascular ring separates ground into pith and cortex in dicots.

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Monocots vs. Dicots• Monocot leaves have parallel veins and

the base of the leaf blade encircles and sheathes the stem; dicots leaves have netlike veins and the flat portion (blade) is usually connected to the stem by a stalk (petiole).

• Monocot flowers typically have parts that occur in threes or groups of threes; dicot floral parts occur in four or fives or multiples or fours or fives.

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Monocot vs. Eudicot

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Monocots (Single cotyledon)Cotyledons act as transfer tissueRoot vascular tissue occurs in ringParallel leaf venation

Eudicots (Two cotyledons)Cotyledons supply nutrients to seedlingsRoot phloem located between xylem armsNetted leaf venation

Monocot vs. Eudicot

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Monocots (Single cotyledon)Cotyledons act as transfer tissueRoot vascular tissue occurs in ringParallel leaf venation

Eudicots (Two cotyledons)Cotyledons supply nutrients to seedlingsRoot phloem located between xylem armsNetted leaf venation

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Flowering Plants: Monocots or Eudicots

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Stem LeafSeed Root Flower

Mo

no

cots

Eu

dic

ots

One cotyledon in seedRoot xylem andphloem in a ring

Leaf veins forma parallel pattern

Flower parts in threesand multiples of three

Root phloem betweenarms of xylem

Leaf veins forma net pattern

Flower parts in fours orfives and their multiples


Two cotyledons in seedVascular bundlesin a distinct ring

Vascular bundlesscattered in stem

Plant Tissues

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Epidermal Tissues

Contain closely packed epidermal cells

Covered with waxy cuticle

Roots contain root hairs

Lower leaf surface contain stomata

Woody plants covered by cork

Modifications of Epidermal Tissue

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a. Root hairs b. Stoma of leaf c. Cork of older stem

20 m

corn seedling

root hairs

enlongating root tip

epidermalcell

chloroplasts

nucleusstoma

guard cell

corkcork cambium

lenticel

periderm

a: © B. Runk/S. Schoenberger/Grant Heilman Photography; b: © J.R. Waaland/Biological Photo Service; c: © Kingsley Stern


Ground Tissue

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Ground tissue forms bulk of a plant

Parenchyma cells:Least specialized and are found in all organs of plant

Can divide and give rise to more specialized cells

Collenchyma cells:Have thicker primary walls

Form bundles underneath epidermis

Flexible support to immature regions of the plant

Ground Tissue Cells

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a. Parenchyma cells b. Collenchyma cells c. Sclerenchyma cells(All): © Biophoto Associates/Photo Researchers, Inc.

50 m 50 m 50 m

Ground Tissue

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Sclerenchyma cells:Have thick secondary walls impregnated with

ligninMost are nonlivingPrimary function is to support mature regions

of the plantFibersSclereids

Ground Tissue

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Sclerenchyma cells:Have thick secondary walls impregnated with

ligninMost are nonlivingPrimary function is to support mature regions

of the plantFibersSclereids

Tissues of Eudicot Root

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EpidermisCortexEndodermis

Casparian StripVascular Tissue

Pericycle

Eudicot Roots

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endodermis

pericycle

phloem

xylem

cortex

epidermis

root hair

xylem ofvascularcylinder

phloem

pericycle

endodermis

Casparianstrip

water andminerals

Zone ofmaturation

Zone ofelongation

Zone ofcell division

root cap

a. Root tip

c. Casparian strip

b. Vascular cylinder

protoderm

procambium

root apical meristemprotected by

root cap

50 m

a(Root tip): Courtesy Ray F. Evert/University of Wisconsin Madison; b: © CABISCO/Phototake

Vascularcylinder

groundmeristem

Branching of Eudicot Root

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endodermis

vascularcylinder

pericycle

cortex

emergingbranch root

epidermis

© Dwight Kuhn; 24.10a: © John D. Cunningham/Visuals Unlimited


Organization of Monocots Roots

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Monocot roots:

Ground tissue of root’s pith is surrounded by vascular ring

Have the same growth zones as eudicot roots, but do not undergo secondary growth

Monocot Root

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epidermis

cortex

endodermis

pericycle

phloem

xylem

pith

vascularcylinder

a.

b.

a: © John D. Cunningham/Visuals Unlimited; b: Courtesy George Ellmore, Tufts University

100 m

Shoot Tip and Primary Meristems

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axillary bud

internode

shoot apicalmeristem

groundmeristemprocambium

protoderm

vascularcambium

primaryxylem

primaryphloem

groundmeristem

procambium

Three Primary Meristems:

Primary Tissues

primary xylemvascular cambiumprimary phloem

protoderm

leaf primordium

pith

cortex

epidermis

pith

cortex

vascular bundles

a. Shoot tip b. Fate of primary meristems


Herbaceous Eudicot Stem

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(Top): © Ed Reschke; (Bottom): Courtesy Ray F. Evert/University of Wisconsin Madison

100 m

epidermis

cortex

vascularbundle

pith

xylem phloemphloem fiber

vascular cambium parenchyma

epidermis

collenchyma

pith50 m

Monocot Stem

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(Top): © CABISCO/Phototake; (Bottom): © Kingsley Stern

epidermis ground tissue

xylem phloemground tissue(parenchyma)

air space

vessel element

companion cell

bundle sheath cells

sieve-tube member

vascularbundle

Secondary Growth of Stems

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epidermis

lenticel

cortex

cortex

primary phloem

primary xylem

primary xylem

Periderm: As a stembecomes woody, epidermisis replaced by the periderm.

cork

secondary xylem

vascular cambium

cork cambium

Vascular cambium:Lateral meristem that willproduce secondary xylemand secondary phloem ineach succeeding year.

secondary xylem

Bark: Includes periderm and alsoliving secondary phloem.Wood: Increases eachyear; includes annualrings of xylem.

vascular cambium

xylem ray

phloem ray

cork cambiumsecondary phloem

secondary phloem

primary phloem

cork

pith

pith

a.

b.

c.

Documents

1 Chapter 24 Flowering Plants: Structure and Function Professor Nearing, Macomb Community College