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Lecture 5 Outline (Ch. 35). Overview - Monocots vs. Dicots II.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 - PowerPoint PPT Presentation
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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
Plant Tissues - Vascular
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)
Plant Tissues - Vascular
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)
Plant Tissues - Ground
2) CollenchymaCollenchyma:
Thick-walled (uneven); living
• Offers support (flexible & strong)
Ground Tissue System (“Body” of Plant):
Collenchyma cells sunflower
Plant Tissues - Ground
3) SclerenchymaSclerenchyma:Thick, hard-walled; Dead
• Offer support (e.g. hemp fibers; nut shells)
Ground Tissue System (“Body” of Plant):
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
Roots – Structure and Development
In maturation zone, Casparian strip forms – waterproof barrier material surrounding vasculature
Roots – Structure and Development
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?)