Tissue systems

Key Concepts:

• What is a kingdom?
• Why study plants?
• What makes a plant a plant?
• The hierarchy of structure – plant cells,

tissues and organs

• Growth
• Primary growth – elongation
• Secondary growth – diameter expansion
• Morphogenesis occurs during growth

Image – Linnaeus

Carolus

Linnaeus

(1707-1778)

The founder of

modern

taxonomy

defined

kingdoms by

morphological

similarity

Linnaeus’ Taxonomic

Hierarchy

Taxonomic Category

Example (taxon)

Kingdom

Plantae, also Metaphyta = all plants

Division (phylum)

Magnoliophyta = all angiosperms

Class

Liliopsida = all monocots

Order

Asparagales = related families

(Orchidaceae, Iridaceae, etc)

Family

Orchidaceae = related genera

(Platanthera,

Spiranthes, etc)

Genus

Platanthera = related species

(P. ciliaris, P.

integra, etc)

Specific name/epithet

ciliaris = one species

Linnaeus’ Taxonomic

Hierarchy

Taxonomic Category

Example (taxon)

Kingdom

Plantae, also Metaphyta = all plants

Division (phylum)

Magnoliophyta = all angiosperms

Class

Liliopsida = all monocots

Order

Asparagales = related families

(Orchidaceae, Iridaceae, etc)

Family

Orchidaceae = related genera

(Platanthera,

Spiranthes, etc)

Genus

Platanthera = related species

(P. ciliaris, P.

integra, etc)

Specific name/epithet

ciliaris = one species

Images – the 3 multicellular kingdoms, animals, fungi and plants

Linnaeus recognized only 2

kingdoms

• If it moved – animal; if it didn’t – plant

• Fungi were lumped with plants

• The microscopic world was largely
unknown

Diagram – 3 domain system of classification

Molecular data supports 3

domain classification scheme

Kingdoms are defined by monophyletic lineage

Diagram – transition from 5 kingdom to 3
domain system indicating dynamic nature of
classification

Classification is Dynamic!

Multicellular eukaryotes remain fairly well

defined – the plants, fungi and animals.

Classification of single celled organisms is still

underway.

Current Taxonomic

Hierarchy

Taxonomic Category

Example (taxon)

Domain

Eukarya = all eukaryotic organisms

Kingdom

Plantae, also Metaphyta = all plants

Division (phylum)

Magnoliophyta = all angiosperms

Class

Liliopsida = all monocots

Order

Asparagales = related families

(Orchidaceae, Iridaceae, etc)

Family

Orchidaceae = related genera

(Platanthera,

Spiranthes, etc)

Genus

Platanthera = related species

(P. ciliaris, P.

integra, etc)

Specific name/epithet

ciliaris = one species

What makes a plant a plant???

• Multicellular, eukaryotic organisms with extensive

specialization

• Almost all are photosynthetic, with chloroplasts (=

green)

 Some obtain additional nutrition through parasitism or carnivory

 Some are saprophytic, entirely without chlorophyll (absorb dead

OM)

• Excess carbohydrates stored as starch (coiled, branched

polymer of glucose)

• Cell walls of cellulose = fibrous (not branched)

polysaccharide = accounts for the relative rigidity of the

cell wall

• Cell division by formation of cell plate

• Most extant plant species are terrestrial (many

characteristics that are adapted for terrestrial life)

• Separated from cyanobacteria by chloroplasts

• Separated from green algae by various adaptations to

terrestrial life

Read this later….

Plants were the first organisms

to move onto land

• Occurred about 475mya
• Very different conditions from former

marine habitat

• Many new traits emerged in

adaptation to life on dry land

• Extensive adaptive radiation into

many new ecological niches

Diagram – phylogeny of land
plants; same on next slide

Four major

groups of

plants have

emerged since

plants took to

land

We will focus

angiosperms

Next semester

in 211 you will

learn more

about the

transition from

water to land,

and the

evolution of

reproductive

strategies in all

plants

Image – chloroplast free
white bracts on white-top
sedge

Critical Thinking

• Do all plant cells

have
chloroplasts???

• How can you tell???

Diagram – primary and
secondary cell walls; same on
next slide

More on the cell wall:

• All cell walls are

produced by the

cell membrane

• Primary wall is

produced first

 Mostly cellulose

• Secondary walls are

produced later

 Lignified, so

• Secondary walls are

interior to primary

walls

Micrographs – plant cell types

Five Major

Plant Cell

Types

• Parenchyma

• Collenchyma

• Sclerenchyma

• Xylem elements

• Phloem

elements

Micrograph – collenchyma
cells; same on next slide

Collenchyma

• Thick primary

wall

• No secondary

wall

Implications???

• Support

growing
tissues

Collenchyma

• Thick primary

wall

• No secondary

wall

Implications???

• Support

growing tissues

Micrograph –
sclerenchma cells;
same on next slide

Sclerenchyma

• Thick secondary wall
• Secondary walls are

lignified

Implications???

• Support mature

plant parts

• Often dead at

maturity

Sclerenchyma

• Thick secondary wall
• Secondary walls are

lignified

Implications???

• Support mature

plant parts

• Often dead at

maturity

Micrographs – collenchyma and sclerenchyma cell comparison

Collenchyma vs. Sclerenchyma

• Both provide structural support
• Both have thick walls
• Collenchyma = thick primary wall, no lignin
• Sclerenchyma = thick secondary wall, lignified

Diagrams and
micrograph –
tracheids and vessel
elements

Xylem

Elements

• Lignified secondary

walls

• Always dead at

maturity (open)

• Function to transport

water and dissolved
nutrients, and to
support the plant

• Tracheids and vessel

elements

Micrograph – rings of lignin in
developing vessel element;
same on next slide

Critical

Thinking

• Vessel elements

and the convergent
evolution of rings

• What else looks

like this????

• What is the

function????

Critical

Thinking

• Vessel elements

and the
convergent
evolution of
rings

• What else looks

like this????

• What is the

function????

Micrograph – phloem elements

Phloem

Elements

• Sieve tube members +

companion cells

• STM lack nucleus,

ribosomes – their

metabolism is controlled

by the companion cells

• Function to transport

the products of

metabolism

• Non-angiosperms have

more primitive phloem

elements

Diagram – phloem elements

Critical Thinking

• What might be the functional

advantage of a cell with no
nucleus???

Micrographs – plant cell types

Plants are

Simple 

Only Five

Major Cell

Types

• Parenchyma

• Collenchyma

• Sclerenchyma

• Xylem elements

• Phloem elements

Micrograph
and diagram
– epidermis

Epidermis Tissue:

• Covers the outer surface of

all plant parts

• Shoot surfaces covered

with waxy cuticle

Helps to protect the plant

and prevent desiccation

• Usually a single,

transparent cell layer

• Tight joints; stomata allow

for gas exchange

Critical Thinking

• Do roots have a waxy cuticle???

• Why or why not???

Never forget the importance

of natural selection!!!!!

Micrograph –
vascular bundle in
cross section

Vascular Tissue:

• Transports water, solutes,

and metabolic products
throughout the plant

• Confers structural

support

• Includes xylem elements,

phloem elements,
parenchyma and
sclerenchyma fibers

Micrograph and diagram –
ground tissues in stems and
leaves

Ground Tissue:

• Bulk of the plant

body – pith, cortex
and mesophyll

• Mostly parenchyma
• Most metabolic,

structural and
storage functions

Micrograph of herbaceous eudicot stem; image of
woody stem; diagram of woody stem tissue
organization

Critical Thinking

• Is this what the inside of a tree looks

like???

Image – new growth at tip of stem

Meristem Tissue:

• How the plant grows
• Cells divide constantly during the

growing season to make new tissues

• More details later

Diagram – plant tissue systems

Plants are

Simple 

Only Four Major

Tissue Types

• Epidermis
• Vascular
• Ground
• Meristem

Tissues Make Organs:

• Roots – anchor the plant, absorb

water and nutrients

• Stems – support the leaves
• Leaves – main site of photosynthesis
• Reproductive organs (flowers, cones,

etc – more later)

All organs have additional functions –

hormone synthesis, transport, etc…

ancestral

paleoherbs

magnoliids

eudicots

monocots

Modern molecular evidence

indicates four classes of

angiosperms

Images – water lily and magnolia

Paleoherbs and Magnoliids comprise

about 3% of angiosperms

Paleoherbs
• Aristolochiaceae,

Nymphaeaceae,
etc

Magnoliids
• Magnoliaceae,

Lauraceae,
nutmeg, black
pepper, etc

ancestral

paleoherbs

magnoliids

eudicots

monocots

Modern evidence indicates 4 classes

of angiosperms

~ 97% of

angiosperm

Images – eudicots

Eudicots include 70+% of all

angiosperms:

• Most broadleaf trees and shrubs
• Most fruit and vegetable crops
• Most herbaceous flowering plants

Monocots vs. Eudicots

Monocots
• Flower parts in

multiples of 3

• Parallel leaf venation
• Single cotyledon
• Vascular bundles in

complex

arrangement

• ~90,000 species

Eudicots
• Flower parts in

multiples of 4 or 5

• Netted leaf venation
• Two cotyledons
• Vascular bundles in a

ring around the stem

• Modern classification

indicates 2 small

primitive groups +

eudicots

• 200,000+ species

Micrographs – cross sections of eudicot and
moncot roots; same on next 3 slides

Root System Tissue

Organization

Eudicots

Monocots

Epidermis, ground, endodermis, pericycle, vascular

tissues

Eudicot root – closeup

Epidermis

Cortex

Endodermis

Pericycle

Vascular
tissues – in
solid core

Monocot root – closeup

Epidermis

Cortex

Endodermis

Pericycle

Vascular tissues –
in ring

Pith in the very
center

Micrograph – eudicot and monocot stem
tissue organization; same on next 4
slides

Stem System Tissue

Organization

Eudicots

Monocots

Epidermis, ground, vascular

tissues

Eudicot stem – closeup

Epidermis

Cortex

Vascular
tissues –
bundles
in a ring

Pith

Stem System Tissue

Organization

Eudicots

Monocots

Monocots cannot make wood

More on wood formation later

Diagram – leaf tissue arrangement

Leaf closeup

Epidermis

Cortex –
palisade
mesophyll

Cortex –
spongy
mesophyll

Vascular
tissues

Diagram – shoot and root systems

See, plants really are simple



• 5 cell types
• 4 tissue types
• 4 organ types

Plant Growth

• Remember, most plants are anchored by

roots

• They can’t move to escape or take

advantage of changes in their
environment

• Plants adjust to their environment
• Simple structure + lots of developmental

flexibility allow plants to alter when and
how they grow

Developmental flexibility comes

from meristems

Meristem Tissues

• Actively dividing cells that generate

all other cells in the plant body

• Cause indeterminate growth

Stems and roots elongate throughout the

plant’s life (indeterminate primary
growth)

Trees continually expand in diameter

(indeterminate secondary growth)

Branches form in roots and stems

Not all plant parts have

indeterminate growth

patterns

Indeterminate:

Roots

and

Stems

These parts grow

throughout the life

of the plant,

exploring new

environments or

responding to

damage

Determinate:

Leaves

Flowers

Fruits

These parts grow

to a genetically +/-

predetermined size

and shape and

then stop – cannot

repair damage

Some mature cells can

de-differentiate to

become meristematic

once more!!!

• Primarily occurs in the indeterminate

parts

Stems and roots

• A process that very seldom occurs in

other kingdoms

• Allows stems and roots to repair damage

and form branches and sprouts

Growth in Plants:

an irreversible increase in size

due to metabolic processes

(processes that use ATP energy)

• Cell division produces new cells =

function of meristem

• Cell expansion increases the size of the

new cells = up to 80% of size increase

• Cell differentiation occurs during and

after expansion

Diagram – planes of cell division and the effect on morphogenesis

The plane of cell division contributes to

morphogenesis

Division in 2 planes forms sheets of cells

Critical Thinking

• What tissues are files of cells???

• What tissues are sheets of cells???

• What tissues are 3-D bulky???

Growth in Plants:

an irreversible increase in size

due to metabolic processes

(processes that use ATP energy)

• Cell division produces new cells =

function of meristem

• Cell expansion increases the size of the

new cells = up to 80% of size increase

• Cell differentiation occurs during and

after expansion

Diagram – cellulose orientation in
primary wall and the effects on
morphogenesis

The direction of cell expansion depends on

cellulose orientation, and contributes to

morphogenesis

Growth in Plants:

an irreversible increase in size

due to metabolic processes

(processes that use ATP energy)

• Cell division produces new cells =

function of meristem

• Cell expansion increases the size of the

new cells = up to 80% of size increase

• Cell differentiation occurs during and

after expansion

Diagram – patterns
of growth in roots

Expansion

and

differentiation

occur in an

overlapping

zone in all

plant parts

REVIEW:

Growth in Plants:

an irreversible increase in size

due to metabolic processes

(processes that use ATP energy)

• Cell division produces new cells =

function of meristem

• Cell expansion increases the size of the

new cells = up to 80% of size increase

• Cell differentiation occurs during and

after expansion

Diagram – location
of meristems on the
plant body; next
slide also

Location of

the

meristems

determines

the pattern

of plant

growth

Most

common

meristems:

apical,

axillary and

lateral

Apical

meristems

cause

elongation of

roots and

stems

Root Cap

• Protects the meristem
• Secretes mucigel

Eases movement of roots through soil
Secretes chemicals that enhance nutrient

uptake

• Constantly shedding cells

Mechanical abrasion as roots grow through

soil

• Constantly being replenished by

meristem

101

Micrograph – root hairs
extending from
epidermis; same on
next few slides

Root Hairs

• Form as the epidermis

fully differentiates

• Extensions off epidermal

cells

 NOT files of cells
 Part of an epidermal cell

• Hugely increase the

surface area of the

epidermis

• 10 cubic cm (double

handful) of soil might

contain 1 m of plant

roots

 Mostly root hairs

104

Root Hairs

• By contrast, 10 cc of soil

may contain up to 1000

m of fungal hyphae

(1km!)

 These serve a similar

function for the fungus

 Ramify throughout the

substrate for maximum

absorption

 Some fungi form symbiotic

associations with plant

roots and both organisms

benefit from this huge

absorptive surface area!

 More in 211…..

105

Diagram – location of apical meristems

Apical

meristems

cause

elongation of

roots and

stems

109

Diagram – meristem locations

Axillary

meristems

allow for

branching –

similar in

structure

and function

to apical

meristems

Remember, pericycle

in roots has same

function

112

As with roots –

cell division

occurs first; zones

of expansion and

differentiation

overlap

Axillary buds may

activate to make

branches, or may

remain dormant

114

Diagram – meristem locations

Lateral

meristems

cause

diameter

expansion

Roots also

expand in

diameter, but it’s

more

complicated –

we’ll save that

for BIOL 300

116

Diagram – primary vs. secondary growth

Remember:

Elongation is

primary growth

Diameter

expansion is

secondary

growth

117

Images – cross section of wood and whole tree

Secondary

growth –

diameter

expansion

118

Micrograph – cross section of a
eudicot stem; same on next 2
slides

Eudicot Stem – recall the

arrangement of vascular

bundles

119

Eudicot Stem – recall the

arrangement of vascular

bundles

Vascular

cambium

forms here:

120

Eudicot Stem – recall the

arrangement of vascular

bundles

Vascular

cambium

forms here:

a cylinder of

meristem

tissue

between the

xylem to the

interior and

the phloem

to the

exterior

121

Diagram – location of the
vascular cambium relative to
other tree tissues

Secondary xylem and phloem form

through cell division by the vascular

cambium

122

Diagram – transition from
primary growth to secondary
growth; same on next slide

During primary
growth the vascular
tissues form in

bundles

from the

apical meristem

During secondary
growth the vascular
tissues form in

cylinders

from the

vascular cambium

xylem to the

inside

phloem to the

outside

128

Bark

• All tissues external to the vascular

cambium

• Diameter expansion splits original

epidermis

Bark structurally and functionally

replaces epidermis

• Inner bark

Functional secondary phloem

• Outer bark

Composition varies as tree matures

130

Cork Cambium

• Meristematic tissue
• Forms in a cylinder during 2

growth

• Divides to produce cork cells

Cells filled with waxy, waterproof suberin

• Eventually cork cambium becomes

cork itself

131

More on cork cambium

• First layer develops from cortex

De-differentiation!!!

• Second layer forms from cortex –

same process

• Third layer forms from cortex…..
• Cortex eventually runs out
• Then what???

132

More on cork cambium

• First layer develops from cortex

De-differentiation!!!

• Second layer forms from cortex –

same process

• Third layer forms from cortex…..
• Cortex eventually runs out
• Then what???

133

More on cork cambium

• First layer develops from cortex

De-differentiation!!!

• Second layer forms from cortex –

same process

• Third layer forms from cortex…..

• Cortex eventually runs out
• Then what???

134

More on cork cambium

• First layer develops from cortex

De-differentiation!!!

• Second layer forms from cortex –

same process

• Third layer forms from cortex…..

• Cortex eventually runs out

• Then what???

135

Diagram – lateral meristems
and the secondary tissues in
a tree; same on next slide

Critical Thinking

• What is the next available layer of

tissue???

137

More on cork cambium

• First layer develops from cortex

De-differentiation!!!

• Second layer forms from cortex –

same process

• Third layer forms from cortex…..
• Cortex eventually runs out
• Then what???

138

More on cork cambium

• First layer develops from cortex

De-differentiation!!!

• Second layer forms from cortex –

same process

• Third layer forms from cortex…..
• Cortex eventually runs out
• Then what???

139

Diagram – how undifferentiated cells develop into the tissues of the plant body

Stem Tissue Derivations and

Fates:

Cells divide, expand and differentiate

140

Review:

Key Concepts:

• What is a kingdom?
• Why study plants?
• What makes a plant a plant?
• The hierarchy of structure – plant cells,

tissues and organs

• Growth
• Primary growth – elongation
• Secondary growth – diameter

expansion

• Morphogenesis occurs during growth

141

Various images and a micrograph of a monocot
stem – an example of one influence of plants on
American history

Monocots, Palmetto Trees,

Ft. Moultrie and the SC State

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