Biology Lab C_FALL

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22-1

Organs and Tissues of

Flowering Plants

22.1 Flowering plants typically have

roots, stems, and leaves

 Most flowering plants possess a:

 Shoot system – stem, branches, leaves, and flowers

(organs of sexual reproduction)

 Root system – main root and its branches

22-2

22-3

Figure 22.1A

stem

internode

petiole

axillary bud

terminal bud

node

Shoot system Root system

node

leaf blade

root tip

vascular tissues

(xylem and phloem)

lateral

branch

root

hairs

primary

root

22.1 Flowering plants typically have

roots, stems, and leaves

 The Stem

 4 main functions

 Supports the leaves and flowers

 Growth of stem

 Transport of water and nutrients between leaves and roots

 Food storage (sometimes)

 Terminal bud in shoot tip

 Produces new leaves and new axillary (lateral) buds

 Axillary buds can produce new branches or flowers

 Node is where a leaf or flower joins the stem

 Internode is the region between the nodes

22-4

22.1 Flowering plants typically have

roots, stems, and leaves

 Leaves

 Usually chief organs of photosynthesis

 Blade – wide portion of a foliage leaf

 Petiole – stalk that attaches blade to stem

 Many specializations

22-5

22-6 Figure 22.1B

stem

leaves

Spines are the leaves of a cactus © Patti Murray/Animals Animals

22-7

tendril

Tendrils are modified leaves of a cucumber © Michael Gadomski/Photo Researchers, Inc

Figure 22.1B (continued)

22-8

Leaves of a Venus flytrap capture insects © Steven P. Lynch

Figure 22.1B (continued)

22.1 Flowering plants typically have

roots, stems, and leaves

 Roots

 Main functions:

1. Anchor plant in soil

2. Absorb water and minerals from soil

3. Produce hormones

 Some also store food

 Root hairs increase surface-to-volume ratio

 Main types of roots:

1. Tap roots

2. Fibrous roots

22-9

22-10 Figure 22.1C

(taproot): © Jonathan Buckley/Getty Images;; (fibrous root): © The McGraw-hill companies Inc./Evelyn Jo Johnson, photographer

Taproot Fibroous root system

22.2 Flowering plants are either

monocots or eudicots

 Monocots have one cotyledon

 Root vascular tissue rings pith

 Vascular bundles scattered in stem

 Leaf veins are parallel

 Flower parts in multiples of three

 Eudicots have two cotyledons

 Root phloem between arms of xylem

 Vascular bundles in distinct ring

 Leaf veins form net pattern

 Flower parts in multiples of four or five

22-11

22-12 Figure 22.2

M o

n o

c o

E u

d ic

o ts

Two cotyledons in seed

Root phloem between

arms of xylem

Vascular bundles

in a distinct ring Leaf veins form

a net pattern

Flower parts in fours or

fives and their multiples

axillary bud

pith

xylem

phloem

One cotyledon in seed

xylem

Seed Root Stem Leaf Flower

endosperm phloem pith

Root xylem and

phloem in a ring Vascular bundles

scattered in stem

axillary bud

Flower parts in threes

and multiples of three

Leaf veins form

a parallel pattern

HOW BIOLOGY IMPACTS OUR LIVES

22A Monocots Serve Humans Well

 Monocots are a small but important group.

 Domestication of monocots included selective

breeding to accumulate desirable traits in crops.

 Corn is the most important crop plant in the U.S.

 Over 50% of the world’s people depend on rice

for about 80% of their calorie requirements.

22-13

22-14 Figure 22A

(rice plants): © Corbis RF; (rice grain head): © Dex Image/Getty RF; (wheat): © Earl Roberge/Photo Researchers, Inc

Rice plants, Oryza

grain head

Wheat plants,Triticum

22-15

(ear of corn): © Doug Wilson/Corbis; (corn plants): © Adam Hart-Davis/SPL/Photo

Researchers, Inc.; (barley plants): © Sundell Larsen/Getty RF; (barley grains): © C.

Sherburne/Photolink/Getty RF

Corn plants, Zea mays Barley

ear

Figure 22A

(continued)

22.3 Plants have specialized cells

and tissues

 Apical meristem

 Located in terminal bud of shoot system and in root tip

 Daughter cells differentiate into one of three primary

meristems:

1. Epidermal tissue forms outer protective covering

2. Ground tissue fills interior plant and serves metabolic

functions

3. Vascular tissue contains xylem and phloem

22-16

22.3 Plants have specialized cells

and tissues

 Epidermal tissue  Epidermis covers entire body of plant

 Waxy cuticle minimizes water loss

 Leaves contain stomata ringed by guard cells  CO2 uptake and water loss

 Roots have root hairs

 Epidermis is replaced by cork in tree trunk  New cork cells are made by cork cambium

 Lenticels function in gas exchange in some trees

22-17

Figure 22.3A 22-18

22.3 Plants have specialized cells

and tissues

 Ground tissue

 Bulk of stems, leaves, and roots

 Three types of cells:

 Parenchyma cells – least specialized type, found in all plant

organs

 Collenchyma cells – thicker primary walls than parenchyma

cells

 Provide structural support in nonwoody plants

 Sclerenchyma cells – thick secondary cell walls

impregnated with lignin

 Makes plant cell walls tough and hard

22-19

22-20

Figure 22.3B

(all): © Biophoto Associates/Photo Researchers, Inc

Parenchyma cells with thin walls

255X 340X

100X

Collenchyma cells

with thicker walls

Sclerenchyma cells

with very thick walls

22.3 Plants have specialized cells and

tissues

 Vascular tissue  Xylem

 Transports water and minerals from roots to leaves

 Contains vessel elements and tracheids

 Phloem  Transports sugar (sucrose), and other organic compounds,

usually from leaves to roots

 Sieve-tube members – conducting cells of phloem are arranged to form continuous sieve tube

 Companion cells

22-21

22-22 Figure 22.3C

a. Xylem micrograph

pits

tracheids

tracheid

end wall

225X c.Tracheids

pitted

walls

vessel

element

b.Two types of vessels

xylem

parenchyma

cell

vessel

element

(Left): © J.R. Waaland/Biological Photo Service

22-23

Sieve-tube member and companion cells Phloem micrograph

companion cell

sieve plate

companion cell

sieve plate

nucleus

phloem

parenchyma cell

sieve-tube

member

sieve-tube

member

450X

(Left): © George Wilder/Visuals Unlimited

Figure 22.3D

22.4 The three types of plant tissues are

present in each organ

 Leaf

 Upper and lower epidermis has outer, waxy cuticle,

which prevents water loss

 Stomata located in lower epidermis

 Interior of leaf is made of mesophyll

 Ground tissue composed of parenchyma cells

 Contain chloroplasts and carry on photosynthesis

 Palisade vs. spongy mesophyll

 Leaf veins branch and terminate in mesophyll

22-24

22.4 The three types of plant tissues are

present in each organ

 Stem

 Herbaceous plants have nonwoody stems

 Ground tissue consists of cortex and central pith

 Vascular bundles

 Ring in eudicot

 Scattered in monocot

 Vascular tissue supports shoot system and

transports food and water

22-25

22.4 The three types of plant tissues are

present in each organ

 Root

 Epidermis usually consists of single layer of cells

 Many epidermal cells have root hairs

 Large, thin-walled parenchyma cells make up cortex,

layer of ground tissue cells located beneath epidermis

 Cortex functions in food storage

 Cells contain starch granules

 Endodermis forms outer tissue of vascular cylinder

 Casparian strip forces water and minerals to pass through

cells

 Pericycle – lateral roots arise from actively dividing cells

22-26

22-27

Figure 22.4A

Stem

Leaf

Root

ground

tissue

epidermal

tissue

vascular

tissue

ground

tissue

ground

tissue

epidermal

tissue

vascular

tissue

vascular

tissue

epidermal

tissue

22-28 Figure 22.4B

a. Leaf

stoma

guard cell

xylem

phloem leaf vein

mesophyll

cuticle

lower

epidermis

upper

epidermis

Xylem transports

water and minerals.

Phloem transports sugar.

epidermal

ground

vascular

Tissue Types

22-29

100 µm

cortex

pith

epidermis

b. Eudicot stem

vascular

bundle

b: © Ed Reschke

epidermal ground vascular

Tissue Types

Figure 22.4B (continued)

22-30

epidermis

c. Monocot stem

cortex

vascular

bundle

c: © CABISCO/Phototake;

epidermal ground vascular

Tissue Types

Figure 22.4B (continued)

22-31

100 µm

cortex

pith

epidermis epidermis

b. Eudicot stem c. Monocot stem

cortex

vascular

bundle vascular

bundle

b: © Ed Reschke; c: © CABISCO/Phototake;

epidermal

ground

vascular

Tissue Types

Figure 22.4B (continued)

22-32

endodermis

epidermis

phloem

xylem

cortex

All tissues

epidermal ground vascular

d. Eudicot root

Tissue Types

vascular

cylinder

d: © CABISCO/Phototake

Figure 22.4B (continued)

22-33

endodermis

epidermis

phloem

xylem

cortex

All tissues

50 µm epidermal ground vascular

d. Eudicot root

Tissue Types

vascular

cylinder

Vascular cylinder d: © CABISCO/Phototake

Figure 22.4B (continued)

22-34

vascular tissue

100 µm

cortex

pith

epidermis epidermis

b. Eudicot stem

a. Leaf

c. Monocot stem

cortex

stoma

guard cell

xylem

phloem leaf vein

mesophyll

cuticle

endodermis

epidermis

phloem

xylem

cortex

All tissues

50 µm

epidermal ground vascular d. Eudicot root

epidermal

tissue

ground

tissue

shoot system

root system

Tissue Types

vascular

cylinder

Vascular cylinder

vascular

bundle vascular

bundle

lower

epidermis

upper

epidermis

Xylem transports

water and minerals.

Phloem transports sugar.

b: © Ed Reschke; c: © CABISCO/Phototake; d: © CABISCO/Phototake

Figure 22.4B

22-35

Growth of Roots and Stems

22.5 Primary growth lengthens the root

and shoot systems

 Primary growth

 Causes plant to grow lengthwise

 Centered in apex (tip) of shoot and root

 Meristem is region of actively dividing cells

 After new cells are produced by mitosis, they go on to

become specialized tissues:

1. Epidermal tissue

2. Ground tissue

3. Vascular tissue

22-36

22.5 Primary growth lengthens the root

and shoot systems

 Root system

 Zone of cell division

 Protected by root cap and sheath

 Contains root apical meristem

 Primary meristems develop into three mature tissue types:

1. Protoderm → epidermis

2. Ground mersitem → ground tissue (cortex)

3. Procambium → vascular tissue

22-37

22.5 Primary growth lengthens the root

and shoot systems

 Root system

 Zone of elongation

 Region where root increases in length due to elongation of

cells

 Cells lengthen but are not fully specialized

 Zone of maturation

 Region that contains fully differentiated cells

 Recognized by root hairs

22-38

22-39

(Right): Courtesy Ray F. Evert/University of Wisconsin Madison

endodermis

phloem

xylem

cortex

epidermis

root hair

Root cap

a. b.

root cap

protoderm

procambium

pericycle

Zone of

elongation Vascular

cylinder

Zone of

cell division ground

meristem

Zone of

maturation

Root apical meristem

protected by

root cap

Figure 22.5A

22.5 Primary growth lengthens the root

and shoot systems

 Shoot system

 Terminal bud includes shoot apical meristem and leaf

primordia (young leaves)

 Leaf primordia fold over apical meristem for protection

 Shoot apical meristem produces everything

 Leaves, axillary buds, additional stem, and sometimes

flowers

 Gives rise to same primary meristems as in root:

1. Protoderm → epidermis of stems and leaves

2. Ground mersitem → cortex, pith, mesophyll

3. Procambium → vascular tissue

 Vascular cambium responsible for secondary growth

22-40

22-41 Figure 22.5B

22.5 Primary growth lengthens the root

and shoot systems

 Shoot system – winter twig

 Changes allow stem to overwinter

 Terminal bud contains apical meristem, and leaf

primordia of shoot tip are protected by terminal bud

scales

 Leaf scars and vascular bundle scars mark spot of

abscission (dropoff)

 Dormant axillary buds can give rise to branches or flowers

found here

 Determine age of stem by counting terminal bud

scale scars

 One for each year’s growth

22-42

22-43

axillary bud

T wig during winter

T wig during spring

leaf scar terminal bud

vascular bundle

scars

terminal bud

scales

terminal bud

scale scar

Figure 22.5C

22.6 Secondary growth widens roots and

stems

 Secondary growth occurs only in woody plants

 Increases girth of trunks, stems, branches, and roots

 Occurs due to the growth of lateral meristems:

vascular cambium and cork cambium

 Woody stem has 3 distinct areas:

1. Bark

2. Wood – secondary xylem that builds up year after

year

3. Pith

22-44

22-45 Figure 22.6A

epidermis

lenticel

primary phloem

primary xylem

secondary xylem

Bark: Includes periderm and also phloem

xylem ray

phloem ray

cork cambium

secondary phloem primary phloem

cork

pith

primary xylem secondary xylem vascular cambium secondary phloem primary phloem cork cambium cork

cortex

Vascular cambium:

Lateral meristem that will

produce secondary xylem

and secondary phloem in

each succeeding year.

Wood: Increases each year; includes annual

rings of xylem

Pith: Parenchyma cells that have a

storage function; becomes

squeezed out by heartwood

22.6 Secondary growth widens roots

and stems

 Bark contains periderm and phloem

 Periderm – secondary growth tissue that contains

cork and cork cambium

 Replaces epidermis

 Cork cambium lies beneath epidermis, but later is

part of periderm

 Cork cambium produces cork cells that disrupt and replace

epidermis

 Cork cells are impregnated with suberin

 Impermeable cork may be interrupted by lenticels

22-46

22-47 Figure 22.6B

cork

sapwood

heartwood

phloem Bark

vascular

cambium

Wood

HOW LIFE CHANGES

22B The First Forests

 Eospermatopteris is woody tree that lived in Devonian

period (over 385 MYA) before animals had invaded land

 9 m* tall and palm tree like

 As soon as modern vascular tissue evolved, so did trees

that could grow taller and wider because they could

transport materials throughout a larger body

 Wood provides structural support a larger plant needs to

remain erect

 Trees help preserve ecological conditions that allow

animals such as humans to live on land

22-48

22-49

Figure 22B.1

Figure 22B.2

22-50

Homeostatic Mechanisms of Plants

22.7 Leaves are organized to carry

on photosynthesis

 Functions of foliage leaf:

 Photosynthesis

 Regulate water loss

 Protection against parasites and predators

 Epidermal tissue on upper and lower surfaces

 Contains trichomes – protective hairs

 Waxy cuticle to prevent water loss

 Stomata allow CO2 gain and water loss

22-51

22.7 Leaves are organized to carry

on photosynthesis

 Mesophyll

 Elongated cells of palisade mesophyll carry on most

photosynthesis

 Loosely packed spongy mesophyll increases amount

of surface area for CO2 gain and water loss

 Leaf veins

 Bring water and minerals to leaves and distribute

products of photosynthesis to other parts of plant

 Bundle sheaths – layers of cells surrounding

vascular tissue

22-52

22-53 Figure 22.7A

22.7 Leaves are organized to carry

on photosynthesis

 Anatomy of plants allows photosynthesis to

occur:

 Vascular tissue brings water and minerals

 CO2 from stomata

 Exposure to solar energy

 Products of photosynthesis maintains

homeostasis

 Epidermis protects plants from invasion

 Closing stomata prevents water loss

22-54

22-55 Figure 22.7B

22-56 Figure 22.7C

22.7 Leaves are organized to carry

on photosynthesis

 Phloem transport

 Source to sink transport

 Plant hormones

 Highly specific chemical signals between plant parts

and cells

 Tropism – growth response toward or away from

particular stimulus

 Defense mechanisms

 Cuticle, epidermal projections, chemical toxins

 Mutualistic relationship of plant roots and fungi

22-57

22-58 Figure 22.7D

sun

immature leaf

plant cells

dead cell

living cell

mature leaf

sugar

pathogenic

microbial

attack

a. Phloem transports

sugar to areas

of need.

b. Hormones cause

plants to bend

toward the light.

d. Plants practice local cell death

as a defense against attack.

c. Plant roots associate

with fungi to acquire minerals.

Connecting the Concepts:

Chapter 22

 Flowering plants adapted to living on land

 Prevention of water loss critical for land plants

 Stomata and cork

 On land, plants had to evolve a way to oppose

the force of gravity

 Sclerenchyma cells, tracheids, and vessel elements.

 Secondary growth

 Means of water uptake and transport

 Root hairs, xylem

22-59