biology sylvia s. mader michael windelspecht chapter 24 flowering plants: structure and organization...

BiologySylvia S. Mader

Michael Windelspecht

Chapter 24 Flowering Plants:

Structure and Organization

Lecture Outline

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Outline

• 24.1 Organs of Flowering Plants

• 24.2 Tissues of Flowering Plants

• 24.3 Organization and Diversity of Roots

• 24.4 Organization and Diversity of Stems

• 24.5 Organization and Diversity of Leaves

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24.1 Organs of Flowering Plants• Flowering plants, or angiosperms, are extremely diverse but

share many common structural features.

• Most flowering plants possess a root system and a shoot system

The root system simply consists of the roots,

The shoot system consists of the stem and leaves.

• A typical plant features three vegetative organs

roots, stems, and leaves

Vegetative organs are concerned with growth and nutrition.

• Flowers, seeds, and fruits are structures involved in reproduction.

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Organization of Plant Body

4

stem

internode

leaf

petiole

blade

axillary bud

terminal bud

node

vascular tissues

root hairs

primaryroot

branchroot

shoot systemroot system

node

vein


Organs of Flowering Plants

• Roots

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

• Anchors plant in soil

• Absorbs water and minerals from the soil

• Produces hormones

Root hairs:

• Projections from epidermal root-hair cells

• Greatly increase absorptive capacity of root

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• Stems Shoot system of a plant is composed of the

stem, branches, and leaves• Stem is the main axis of a plant that elongates and

produces leaves– Nodes occur where leaves are attached to the stem– Internode is region between nodes– Axillary buds can produce new branches of the stem (or

flowers)

• Stem also has vascular tissue that transports water and minerals

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• Leaves major part of the plant that carries on

photosynthesis• Foliage leaves are usually broad and thin

– Blade - Wide portion of foliage leaf– Petiole - Stalk attaching blade to stem– Leaf Axil - Upper acute angle between petiole and stem

where the axillary bud is found

• Tendrils - Leaves that attach to objects• Bulbs - Leaves that store food

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Vegetative Organs of Several Eudicots

8

blade

petiole

c. Leaves, pumpkin seedlingb. Shoot system, bean seedlinga. Root system, dandelion

lateral root

roots

stem

stems

a: © Dorling Kindersley/Getty Images; b:© Dwight Kuhn; c: © Dwight Kuhn



• Monocots (Single cotyledon) Cotyledons act as transfer tissue

• Nutrients are derived from the endosperm Root vascular tissue occurs in ring Parallel leaf venation Flower parts arranged in multiples of three

• Eudicots (Two cotyledons) Cotyledons supply nutrients to seedlings Root phloem located between xylem arms Netted leaf venation Flower parts arranged in multiples of four or five

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Flowering Plants are Either 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

24.2 Tissues of Flowering Plants

• Meristematic tissue enables flowering plants to grow throughout their lifetime

• Apical meristems at the tips of stems and roots increase the length of these tissues

• Apical meristem produces three types of meristem, which produce three specialized tissues Epidermal tissue Ground tissue Vascular tissue

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12

Tissues of Flowering Plants

• Epidermal Tissue Forms the outer protective covering of a plant Epidermis contains closely packed epidermal cells

• Epidermal cells exposed to air are covered with waxy cuticle

• Root epidermal cells have root hairs• Epidermal cells of stems, leaves, and reproductive

organs have trichomes• Lower leaf surface contains stomata

In older woody plants, the epidermis of the stem is replaced by periderm

• Major component is cork• New cork is made by cork cambium

Modifications of Epidermal Tissue

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corn seedling

root hairs

enlongatingroot tip

a. Root hairs

guard cell chloroplasts

b. Stoma of leaf

Stomanucleus

lenticel

periderm

corkcork cambium

c. Cork of older stem

a: © Evelyn Jo Johnson; b: © J.R. Waaland/Biological Photo Service; c: © Kingsley Stern


• Ground tissue forms bulk of a flowering 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

• Provide flexible support for immature regions of the plant

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Ground tissue (continued)• Sclerenchyma cells:

– Have thick secondary walls impregnated with lignin

– Most are nonliving– Primary function is to support mature regions of

the plant– Two types of sclerenchyma cells

» Fibers» Sclereids

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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


• Vascular Tissue Xylem transports water and minerals from the

roots to the leaves• Tracheids

– Long, with tapered ends– Water moves across pits in end walls and side

walls– Vascular rays between rows of tracheids

conduct water across the width of the plant• Vessel Elements

– Larger, with perforated plates in their end walls– Form a continuous vessel for water and mineral

transport

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Xylem Structure

18


a. Xylem micrograph (left) and drawing (to side)

pits

vesselelement

tracheids

tracheid

pittedwalls

xylemparenchyma

cell

perforationplate

c. Tracheids

vesselelement

a: © J. Robert Waaland/Biological Photo Service

50 m

b. T wo types of vessels


• Vascular Tissue Phloem transports sucrose and other organic

compounds from the leaves to the roots • Sieve-tube members function as conducting cells

– Contain cytoplasm, but lack nuclei– Sieve plate – cluster of pores in wall

• Each sieve-tube member has a companion cell– Plasmodesmata connect the two– Companion cell contains a nucleus

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Phloem Structure

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a: © George Wilder/Visuals Unlimited

b. Sieve-tube member and companion cells

nucleus

sieve plate

sieve plate

sieve-tube member

companion cell

a. Phloem micrograph (left) and drawing (to side)

phloemparenchyma

cells

sieve-tubemember

companioncell

20 m

24.3 Organization and Diversity of Roots

• Root cap contains root apical meristem

• Zone of cell division contains primary meristems

• Zone of elongation contains cells that are lengthening and becoming specialized

• Zone of maturation contains fully differentiated cells

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Organization and Diversity of Roots

• Tissues of a Eudicot Root: Epidermis - outer layer of root Cortex – composed of parenchyma cells

allowing water and minerals movement Endodermis – forms a boundary between

cortex and inner vascular cylinder• Casparian strip

Vascular Tissue - contains xylem and phloem• Pericycle – mitotically active and can begin

development of branch or lateral roots

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Eudicot Roots

23


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

root cap

Zone ofelongation

Zone ofmaturation

Vascularcylinder

endodermis

pericycle

phloem

xylemcortex

epidermis

root hair

a. Root tip

root apical meristemprotected by

root cap

procambium

protoderm

groundmeristem

c. Casparian strip

pericycle

xylem ofvascularcylinder

Casparianstrip

endodermisphloem

water andminerals

b. Vascular cylinder

50 µm

Zone ofcell division

Branching of Eudicot Root

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endodermis

vascularcylinder

pericycle

cortex

emergingbranch root

epidermis

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



• 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

Have pericycle, endodermis, cortex, and epidermis

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Monocot Root

26


epidermis

cortex

endodermis

pericycle

phloem

xylem

pith

vascularcylinder

a.

b.

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

100 m


• 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

• Adventitious roots - Roots develop from organs of the shoot system instead of the root system

Prop roots27


• Haustoria: Found in parasitic plants Rootlike projections that grow into host plant Make contact with vascular tissue of the host plant

and extract water and nutrients

• Mycorrhizae: Mutualistic associations between roots and fungi Assist in water and mineral extraction

• Root nodules Contain nitrogen-fixing bacteria

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Root Diversity

29


a. Taproot b. Fibrous root system

d. Pneumatophores of blackmangrove trees

c. Prop roots ,a type of adventitious root

e. Aerial roots of English ivy clinging to tree trunks

(a): © Dr. Robert Calentine/Visuals Unlimited; (b): © Evelyn Jo Johnson; (c): © David Newman/Visuals Unlimited; (d): © Alan and Linda Detrick/Photo Researchers, Inc.;(e) left: © David Sieren/Visuals Unlimited; (e) right: © Professor David F. Cox, Lincoln Land Community College

24.4 Organization and Diversity of Stems

• Shoot apical meristem Produces new cells that elongate and

increase stem length Protected by terminal bud

• Enveloped by leaf primordia• Specialized primary meristems

– Protoderm – gives rise to the epidermis– Ground Meristem – gives rise to pith and cortex– Procambium – produces primary xylem and

phloem

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Woody Twig

31


terminal bud

bud scale

one year'sgrowth

terminal bud scale scars

nodeinternode

axillary budleaf scar

stem

bundle scars

node

lenticel

Shoot Tip and Primary Meristems

32

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


Organization and Diversity of Stems

• Herbaceous Stems

Mature non-woody stems exhibit only primary growth

• Outermost tissue covered with waxy cuticle

• Stems have distinctive vascular bundles

– Herbaceous eudicots - Vascular bundles arranged in distinct ring

– Monocots - Vascular bundles scattered throughout stem33

Herbaceous Eudicot Stem

34


epidermis

cortex

pith

100 µm

pith vascular cambium

collenchyma

parenchyma50 µm

epidermis

phloem fiber

phloemxylem

Left: © Ed Reschke; Right: Courtesy Ray F. Evert/University of Wisconsin Madison

vascularbundle

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


• Woody Stems

Woody plants have both primary and secondary tissues

• Primary tissues formed each year from primary meristems

• Secondary tissues develop during first and subsequent years from lateral meristems

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• Woody stems have both primary and secondary growth Primary growth increases the length of the plant

Secondary growth increases the girth

• Woody stems have no vascular tissue, and instead have three distinct regions Bark

Wood

Pith

37

Secondary Growth of Stems

38


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.


• Bark

Bark of a tree contains cork, cork cambium, and phloem

Bark can be removed, but it is harmful to the plant due to lack of organic nutrient transport

Cork cells are impregnated with suberin

• Gas exchange is impeded except at lenticels39


• Wood

Wood is secondary xylem that builds up year after year

• Vascular cambium is dormant during winter

• Annual ring is made up of spring wood and summer wood

In older trees, inner annual rings, called heartwood, no longer function in water transport

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Three-year-old Woody Twig

41

primary xylem

secondaryxylem

springwood

Pith

Wood

Bark

annualring

phloem

phloem ray

cortex

cork

cork cambium

summerwood

Vascular Cambium


© Ed Reschke/Peter Arnold, Inc.

Tree Trunk

42


annual rings

b. Tree trunk, longitudinal view

a. Tree trunk, cross-sectional view

heart wood

sap wood

vascularcambium

phloem

cork

a: © Ardea London Limited


• Stem Diversity Above ground vertical stems Stolons

• Above ground horizontal stems• Produce new plants when nodes touch the ground

Rhizomes• Underground horizontal stems• Contribute to asexual reproduction• Variations:

– Tubers - Enlarged portions functioning in food storage

– Corms - Underground stems that produce new plants during the next season

43

Stem Diversity

44


a: © The McGraw-Hill Companies Inc./Evelyn Jo Johnson, photographer; b: © Science Pictures Limited/Photo Researchers, Inc.;c: © The McGraw Hill Companies, Inc./Carlyn Iverson, photographer; d: © The McGraw Hill Companies, Inc./Carlyn Iverson, photographer

stolon

node

adventitiousroots

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

adventitious roots

paperyleaves

axillarybud

corm

rhizome

rhizome

adventitious roots

axillarybud

tuber

branch

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24.5 Organization and Diversity of Leaves

• Leaves contain: Upper and lower epidermis

• Waxy cuticle• Trichomes• Lower epidermis has stomata for gas exchange

Mesophyll• Eudicot leaves have

– Palisade mesophyll containing elongated cells

– Spongy mesophyll containing irregular cells bounded by air spaces

• Contains many chloroplasts

Leaf Structure

46


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.

Organization and Diversity of Leaves

• Leaf Diversity

Blade of a leaf can be simple or compound

Leaves are adapted to environmental conditions

• Shade leaves

• Spines

• Climbing leaves47

Classification of Leaves

48

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


Leaf Diversity

49


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

biology sylvia s. mader michael windelspecht chapter 24 flowering plants: structure and organization...

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