Lecture 5 Outline (Ch. 35)

Lecture 5 Outline (Ch. 35)I. Overview - Monocots vs. DicotsII. Plant tissues

A. Dermal B. Vascular C. Ground

Cell Types: Parenchyma, Collenchyma, Sclerenchyma

III. Plant organs A. Roots B. Stems C. Leaves

IV. Plant Growth A. Meristems B. Primary vs. secondary

i. Leavesii. Stemsiii. Roots

V. Preparation for next lecture

Plant Classification – Monocots vs. Dicots

Basic categories of plants based on structure and function

Plant “bodies”

Three Basic Plant Organs:

Roots, Stems, and Leaves

Plants, like multicellular animals, have organs composed of different tissues, which in turn are composed of cells

Shootsystem

Leaf

Stem

Rootsystem

Setting the scene - animal bodies

Organs TissuesCells

• Each plant organ has dermal, vascular, and ground tissues

• Each of these three categories forms a tissue system

Plant Tissues

Dermaltissue

Groundtissue Vascular

tissue

1) Dermal Tissue System• Outer covering• Protection

3) Ground Tissue System • “Body” of plant• Photosynthesis; storage; support

2) Vascular Tissue System• “Vessels” throughout plant• Transport materials

Plant Tissues

What type of tissue transports fluids in plants?

A. DermalB. RootsC. VascularD. StemsE. Ground

Dermal Tissue System (Outer Covering of Plant):

1) Epidermal Tissue (epidermis):• Outermost layer

Cuticle: Waxy covering• Reduces evaporation/predation

Root Hairs: extended root surface• Increase absorption

2) Peridermal Tissue (periderm):• Only in woody plants (“bark = dead cells”)• Protection; support

Plant Tissues - Dermis

Plant Tissues - DermisSpecial Dermal Cells – Trichomes & Root hairs

• Trichomes– Hairlike outgrowths of

epidermis – Keep leaf surfaces cool

and reduce evaporation

• Roots hairs– Tube extensions from

epidermal cells– Greatly increase the root’s

surface area for absorption

Guard cells

Stoma

Epidermal cell

Guard cells

Stomata

Epidermal cell

Guard cells

Stoma

Epidermal cell

Guard cells

Stomata

Epidermal cell

4 µm 200 µm

71 µm

a. c.

b.

Plant Tissues - Dermis

Paired sausage-shaped cellsFlank a stoma – epidermal

opening• Passageway for oxygen,

carbon dioxide, and water vapor

Special Dermal Cells – Guard Cells

1) Xylem (dead at maturity) cells:

Plant Tissues - Vascular

A) Tracheids: Narrow, tube-like cellsB) Vessel Elements: Wide, tube-like cells

Vascular Transport System1) Xylem (dead at maturity):

- Moves water & minerals from roots to shoots


A) Sieve Tubes: Wide, tube-like cellsB) Companion Cells: support and regulate

sieve tubes

2) Phloem (living at maturity) cells:Plant Tissues - Vascular

Vascular Transport System

- Moves water, sugar, amino acids & hormones2) Phloem (living at maturity)


Dicots Monocots

Vasculature - ComparisonsMonocots and dicots differ in the arrangement of

vessels in the roots and stems

Root

Stem

• Some major types of ground cells:– Parenchyma– Collenchyma– Sclerenchyma

Plant Tissues – Ground Tissue

• Tissues that are neither dermal nor vascular are ground tissue

• Ground tissue internal to the vascular tissue is pith; ground tissue external to the vascular tissue is cortex

• Ground tissue includes cells specialized for storage, photosynthesis, and support

Plant Tissues - Ground

Ground Tissue System (“Body” of Plant):

1) ParenchymaParenchyma (most abundant):

• plant metabolism:

Photosynthesis; hormone secretion; sugar storage

Thin-walled cells; living

Parenchyma cells in Elodea leaf,(w/chloroplasts)


2) CollenchymaCollenchyma:

Thick-walled (uneven); living

• Offers support (flexible & strong)


Collenchyma cells sunflower


3) SclerenchymaSclerenchyma:Thick, hard-walled; Dead

• Offer support (e.g. hemp fibers; nut shells)


Sclereid cells in pear (LM)

Fiber cells in ash tree

Cell wall

Which is a plant cell type?

A. GroundB. PithC. Sieve-tubesD. CortexE. Stem

Cell types Tissue Types Organ Types

Parenchyma Ground Stems

Collenchyma Vascular Shoots (& flowers)

Sclerenchyma Dermal RootsTracheidsVessels elementsSieve-tubesCompanion cellsEpidermalGuard cells

Self-Check

• Roots need sugars from photosynthesis; • Shoots rely on water and minerals

absorbed by the root system

Roots - Overview

• Root Roles:- Anchoring the plant- Absorbing minerals and water- Storing organic nutrients

Taproots: Fibrous roots:

Typical of dicots, primary root forms and small branch roots grow from it

In monocots mostly, primary root dies, replaced by new roots from stem

Roots - Comparisons

Roots – Structure and Development

• Four regions:– Root capProtection, gravity detection

– Zone of cell divisionMitotic divisions

– Zone of elongationCells lengthen, no division

– Zone of maturationCells differentiate, outer layer

becomes dermis


In maturation zone, Casparian strip forms – waterproof barrier material surrounding vasculature


1250 µm

Epidermis

Primary phloem

Primary xylem

Pith

Mon

ocot

Eudi

cot

Endodermis

Cortex

Epidermis

Primary xylem

Pericycle

Primary phloem

48 µm

385 µm

8 µm

EndodermisLocation ofCasparian strip

EndodermisLocation ofCasparian strip

Cortex

Pericycle

Prop roots

“Strangling”aerial roots

Storage roots

Buttress roots

Pneumatophores

Roots – Many Plants Have Modified Roots

Water storage

Stem: an organ made of– An alternating system of

nodes, points at which leaves attach

– Internodes, stem length between nodes

Stems - Overview

• Axillary bud - structure that can form a lateral shoot, or branch

• Apical/terminal bud - located near the shoot tip, lengthens a shoot

• Apical dominance maintains dormancy in most nonapical buds

Apical bud

NodeInternode

Apicalbud

Shootsystem

Vegetativeshoot

Axillarybud

Stem

Phloem Xylem

Sclerenchyma(fiber cells)

Ground tissueconnectingpith to cortex

Pith

Cortex

1 mm

EpidermisVascularbundle

Cross section of stem with vascular bundles forminga ring (typical of eudicots)

(a)

Keyto labels

DermalGroundVascular

Cross section of stem with scattered vascular bundles(typical of monocots)

(b)1 mm

Epidermis

Vascularbundles

Groundtissue

• In most monocot stems, the vascular bundles are scattered throughout the ground tissue, rather than forming a ring

Vasculature - Stems

Dicot Monocot

Stems – Structure and Development

• Stems have all three types of plant tissue

• Grow by division at meristems– Develop into leaves, other

shoots, and even flowers

• Leaves may be arranged in one of three ways

Rhizomes

Bulbs

Storage leavesStem

Stolons

Stolon

Tubers

Stems – Many Plants Have Modified Stems

The leaf is the main photosynthetic organ of most vascular plants

Leaves - Overview

Shootsystem

LeafBladePetiole

Leaves generally have

a flattened blade

and a stalk called the petiole, which joins the leaf to a node of the stem

Leaves – Structure and Development

• Leaves are several layers thick – each with different cell types

Leaves – Structure and Development

• Most dicots have 2 types of mesophyll– Palisade mesophyllhigh photosynthesis

– Spongy mesophyllair spaces for gas

& water exchange

• Monocot leaves have 1 type of mesophyll

Leaves

• Leaf epidermis contains stomata - allow CO2 exchange • Stomata flanked by two guard cells, control open vs. closed

Keyto labels

DermalGroundVascular

Cuticle Sclerenchymafibers

Stoma

Bundle-sheathcell

XylemPhloem

(a) Cutaway drawing of leaf tissuesGuardcells

Vein

Cuticle

Lowerepidermis

Spongymesophyll

Palisademesophyll

Upperepidermis

Guardcells

Stomatalpore

Surface view of a spiderwort(Tradescantia) leaf (LM)

Epidermalcell

(b)

50 µ

m10

0 µm

Vein Air spaces Guard cellsCross section of a lilac(Syringa)) leaf (LM)

(c)

Most dicots have branch-like veins and palmate leaf shape

Monocots have parallel leaf veins and longer, slender blades

Leaves - Comparisons

Monocots and dicots differ in the arrangement of veins, the vascular tissue of leaves

Tendrils

Spines

Storageleaves

Reproductive leaves

Bracts

Leaves – Plants have modified leaves for various functions

Plant Growth:

1) Indeterminate: Grow throughout life

2) Growth at “tips” (length) and at “hips” (girth)

Growth patterns in plant:

1) Meristem Cells: Dividing Cells

2) Differentiated Cells: Cells specialized in structure & role

• Form stable, permanent part of plant

Plant Growth

1) Primary Growth:

1) Increased length 2) Specialized structures (e.g. fruits)

2) Secondary Growth:

Responsible for increases in stem/root diameter

• Apical Meristems: Mitotic cells at “tips” of roots / stems

• Lateral Meristems: Mitotic cells “hips” of plant

Plant Growth

girth

length

Shoot apical meristem Leaf primordia

Youngleaf

Developingvascularstrand

Axillary budmeristems

Plant Growth

Shoot tip (shootapical meristemand young leaves)

Lateral meristems:

Axillary budmeristem

Vascular cambiumCork cambium

Root apicalmeristems

Primary growth in stems

Epidermis

Cortex

Primary phloem

Primary xylemPith

Secondary growth in stems

PeridermCorkcambium

Cortex

Primaryphloem

Secondaryphloem

PithPrimaryxylemSecondaryxylem

Vascular cambium

Plant GrowthTwo lateral meristems: vascular cambium and cork cambium

Stem – Secondary Growth:• thicker, stronger stemsVascular Cambium: between primary xylem and phloem

primary phloemvascular cambium

primary xylem

epidermis

cortexpith

primary xylem

primary phloem

dividingvascularcambium

Plant Growth

Produces inside stem:A) Secondary xylem

- moves H2O, inwardB) Secondary phloem

- moves sugars, outward

Plant Growth

primaryphloem

dividingvascularcambium

newsecondaryxylem

newsecondaryphloem

primaryxylem

secondary phloemprimary phloem

vascular cambium

primary xylemsecondary xylem

pithcortex

Secondary growthVascular Cambium:

Vascular cambium Growth

Secondaryxylem

After one yearof growth

After two yearsof growth

Secondaryphloem

VascularcambiumX X

X X

X

X

P P

P

P

C

C

C

C

C

C

C C C

C C

CC

Stem – Secondary Growth:

Dead at maturityProtection

Cork Cambium:• Located under outer surface; produces periderm

Plant Growth

GrowthringVascularray

Secondaryxylem

Heartwood

Sapwood

Bark

Vascular cambium

Secondary phloem

Layers of periderm

annual ring

earlyxylem

latexylem

heartwood(xylem)sapwood(xylem)vascularcambium

phloem

Stem – Secondary Growth:

Sapwood = Young xylem, waterHeartwood = Old xylem, supportSeasonal Growth = annual ringsSecondary phloem = grows outward

older phloem crushed

Plant Growth

RESULTS

Rin

g-w

idth

inde

xes

2

1.5

0.5

1

01600 1700 1800 1900 2000

Year

Plant Growth

Using dendrochronology to study climate

Plant Growth

Living tree or dead tree?

A cross section of what tissue is pictured?

A. Monocot rootB. Dicot rootC. Monocot stemD. Dicot stem

Things To Do After Lecture 5…Reading and Preparation:1. Re-read today’s lecture, highlight all vocabulary you do not

understand, and look up terms.2. Ch. 35 Self-Quiz: #1, 3, 6, 7 (correct answers in back of book)3. Read chapter 35, focus on material covered in lecture (terms,

concepts, and figures!)4. Skim next lecture.

“HOMEWORK” (NOT COLLECTED – but things to think about for studying):1. Compare and contrast monocots and dicots.2. List the different types of plant cells and describe which tissues and

organs they make up, including roles for each organ.3. Explain the different between apical and lateral meristems and how

growth occurs.4. Discuss the composition of bark and it’s function for plants (do all plants

have this tissue?)

Lecture 5 Outline (Ch. 35)

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Transcript of Lecture 5 Outline (Ch. 35)