PowerLecture:PowerLecture:Chapter 35Chapter 35

Plant Growth & DevelopmentPlant Growth & Development

Success of the AngiospermsSuccess of the Angiosperms

The angiosperms are seed-bearing The angiosperms are seed-bearing vascular plantsvascular plants

In terms of distribution and diversity, they In terms of distribution and diversity, they are the most successful plants on Earthare the most successful plants on Earth

The structure and function of this plant The structure and function of this plant group help explain its successgroup help explain its success

Shoots and RootsShoots and Roots

Shoots Shoots Produce food by photosynthesisProduce food by photosynthesis Carry out reproductive functionsCarry out reproductive functions

Roots Roots Anchor the plantAnchor the plant Penetrate the soil and absorb water and Penetrate the soil and absorb water and

dissolved mineralsdissolved minerals Store foodStore food

Shoot Apical Meristem

primary meristems active

epidermis, ground tissues, primary vascular tissues forming

epidermis, ground tissues, primary vascular tissues

forming

primary meristems

active

Root Apical Meristem

Fig. 29-3a, p.494

Protoderm

Ground meristem

Procambium

epidermis

ground tissues

primary vascular tissues

a The cellular descendants of apical meristems divide, grow, and differentiate. They form three primary meristems, the activity of which lengthens shoots and roots:

vascular cambium

cork cambium

Lateral Meristems

thickening

Angiosperm Angiosperm Body PlanBody Plan

VASCULAR TISSUES

GROUND TISSUES

SHOOT SYSTEM

ROOT SYSTEM

EPIDERMIS

Ground tissue Ground tissue systemsystem

Vascular tissue Vascular tissue systemsystem

Dermal tissue Dermal tissue system system

Fig. 29-2, p.494

Simple TissuesSimple Tissues

Made up of only one Made up of only one type of celltype of cell

ParenchymaParenchyma

CollenchymaCollenchyma

SclerenchymaSclerenchyma

Cutting SpecimensCutting Specimens

transverse

radial

tangential

Parenchyma: A Simple TissueParenchyma: A Simple Tissue

Most of a plant’s soft primary growthMost of a plant’s soft primary growth Pliable, thin walled, many sided cellsPliable, thin walled, many sided cells Cells remain alive at maturity and retain Cells remain alive at maturity and retain

capacity to dividecapacity to divide Mesophyll is a type that contains Mesophyll is a type that contains

chloroplastschloroplasts

stem epidermis

simple and complex tissues inside the stem

parenchymavessel of

xylem phloem

fibers of sclerenchyma

Fig. 29-6, p.496

Collenchyma: A Simple TissueCollenchyma: A Simple Tissue

Specialized for support for primary Specialized for support for primary tissuestissues

Makes stems strong but pliableMakes stems strong but pliable Cells are elongatedCells are elongated Walls thickened with pectinWalls thickened with pectin Alive at maturityAlive at maturity

Sclerenchyma: A Simple TissueSclerenchyma: A Simple Tissue

Supports mature plant partsSupports mature plant parts Protects many seedsProtects many seeds Thick, lignified walls Thick, lignified walls Dead at maturityDead at maturity Two types:Two types:

Fibers: Long, tapered cellsFibers: Long, tapered cells Sclereids: Stubbier cellsSclereids: Stubbier cells

collenchyma parenchyma lignified secondary wall

Fig. 29-7, p.496

Complex TissuesComplex Tissues

Composed of a mix of cell typesComposed of a mix of cell types

XylemXylem

PhloemPhloem

EpidermisEpidermis

XylemXylem

Conducts water Conducts water

and dissolved and dissolved mineralsminerals

Conducting cells Conducting cells are dead and are dead and hollow at maturityhollow at maturity

vessel membertracheids

one cell’s wall

pit in wall

sieve plate of sieve

tube cell

companion cell

a bc

Fig. 29-8, p.497

Phloem: Phloem: A Complex Vascular TissueA Complex Vascular Tissue

Transports sugars Transports sugars Main conducting Main conducting

cells are sieve-cells are sieve-tube memberstube members

Companion cells Companion cells assist in the assist in the loading of sugarsloading of sugars

sieve plate

sieve-tubemember

companioncell

Epidermis: Epidermis: A Complex Plant TissueA Complex Plant Tissue

Covers and protects plant Covers and protects plant

surfacessurfaces

Secretes a waxy, waterproof Secretes a waxy, waterproof

cuticlecuticle

In plants with secondary growth, In plants with secondary growth,

periderm replaces epidermisperiderm replaces epidermis

leaf surface cuticle epidermal cellphotosynthetic

cell

Fig. 29-9, p.497

MeristemsMeristems

Regions where cell divisions Regions where cell divisions produce plant growthproduce plant growth

Apical meristemsApical meristems Lengthen stems and rootsLengthen stems and roots Responsible for Responsible for primaryprimary growth growth

Lateral meristemsLateral meristems Increase width of stemsIncrease width of stems Responsible for Responsible for secondarysecondary growth growth

Apical Apical MeristemsMeristems

activity atmeristems

new cellselongateand start todifferentiateinto primarytissues

activity atmeristems

new cellselongateand start todifferentiateinto primarytissues

Root apical meristem

Shoot apical meristem

immature leaf

shoot apical meristem

lateral bud forming

vascular tissues

pith

cortex

Fig. 29-10a2, p.498

immature leaf

shoot apical meristem

descendant meristems (orange)

b Sketch of the shoot tip, corresponding to (a) Fig. 29-10b, p.498

Tissue DifferentiationTissue Differentiation

Protoderm Protoderm

Ground meristemGround meristem

ProcambiumProcambium

EpidermisEpidermis

Ground tissueGround tissue

Primary vascular tissuePrimary vascular tissue

Lateral MeristemsLateral Meristems

Increase girth of older roots and stemsIncrease girth of older roots and stems Cylindrical arrays of cellsCylindrical arrays of cells

vascular cambiumcork cambium

thickening

Figure 29.20.aPage 504

Shoot Shoot DevelopmentDevelopment

immature leaf

ground meristem

primary phloem

primary xylempith

procambium

cortex

procambium

protoderm

shoot apical meristem

procambium

epidermis

Figure 29.10 Page 498

immature leaf

shoot apical meristemdescendant meristems (orange)

Stepped Art

Fig. 29-10b-d, p.498

primary phloem

primary xylempith

cortex

Tissue DifferentiationTissue Differentiation

Vascular cambiumVascular cambium

Cork cambiumCork cambium

Secondary vascular tissueSecondary vascular tissue

PeridermPeriderm

Internal Structure of a Internal Structure of a Dicot StemDicot Stem

Outermost layer is epidermisOutermost layer is epidermis Cortex lies beneath epidermisCortex lies beneath epidermis Ring of vascular bundles Ring of vascular bundles

separates the cortex from the separates the cortex from the pith pith

The pith lies in the center of The pith lies in the center of the stemthe stem Figure 29.11.a

Page 499

Internal Internal Structure Structure

of a of a Monocot Monocot

StemStem

• The vascular bundles

are distributed

throughout the ground

tissue

• No division of ground

tissue into cortex and

pith

Figure 29.11.bPage 499

cortex

epidermis

vascular bundle

pith

vessel in xylem

meristem cell

sieve tube in phloem

companion cell in

phloem

Fig. 29-11a, p.499

epidermis

vascular bundle

pith

vessel in xylemcollenchyma

sheath

sieve tube in phloem

companion cell in

phloem

air space

Fig. 29-11b, p.499

Common Leaf FormsCommon Leaf Forms

petiole

blade

axillarybud

node

blade

sheath

node

DICOT MONOCOT

Figure 29.12.a,bPage 500

Adapted for PhotosynthesisAdapted for Photosynthesis

Leaves are usually thin Leaves are usually thin High surface area-to-volume ratio High surface area-to-volume ratio Promotes diffusion of carbon dioxide in, Promotes diffusion of carbon dioxide in,

oxygen outoxygen out

Leaves are arranged to capture sunlightLeaves are arranged to capture sunlight Are held perpendicular to rays of sunAre held perpendicular to rays of sun Arranged so they don’t shade one anotherArranged so they don’t shade one another

POPLAR (Populus)

OAK (Quercus)

MAPLE (Acer)

leaflet

RED BUCKEYE (Aesculus)

BLACK LOCUST (Robina)

HONEY LOCUST (Gleditsia)

Fig. 29-12c,d, p.500

Leaf StructureLeaf Structure

UPPEREPIDERMIS

PALISADEMESOPHYLL

SPONGYMESOPHYLL

LOWEREPIDERMIS

one stoma

cuticle

O2CO2

xylem

phloem

Figure 29.14.bPage 501

leaf blade

leaf vein

stem

Leaf Vein(one vascular bundle) cuticle

Upper Epidermis

Lower Epidermis

Palisade Mesophyll

Spongy Mesophyll

50m

xylem

phloem

cuticle-coated cell of lower epidermis

one stoma (opening across epidermia)

Oxygen and water vapor diffuse out of leaf at stomata.

Carbon dioxide in outside air enters leaf at stomata.

Water, dissolved mineral ions from roots and stems move into leaf vein (blue arrow)

Photosynthetic products (pink arrow) enter vein, will be transported throughout plant body

Fig. 29-14, p.501

Mesophyll:Mesophyll:Photosynthetic TissuePhotosynthetic Tissue

A type of parenchyma tissueA type of parenchyma tissue

Cells have chloroplasts Cells have chloroplasts

Two layers in dicotsTwo layers in dicots Palisade mesophyll Palisade mesophyll

Spongy mesophyll Spongy mesophyll

Leaf Veins: Vascular BundlesLeaf Veins: Vascular Bundles

Xylem and phloem; often Xylem and phloem; often

strengthened with fibers strengthened with fibers

In dicots, veins are netlikeIn dicots, veins are netlike

In monocots, they are parallelIn monocots, they are parallel

Fig. 29-15a, p.501

Leaf VeinsLeaf Veins

Fig. 29-15b, p.501

Leaf Leaf VeinsVeins

Root SystemsRoot Systems

Taproot system of a California poppy

Fibrous root system of a grass plant

Figure 29.19Page 503

Root StructureRoot Structure

Root cap covers tipRoot cap covers tip Apical meristem produces Apical meristem produces

the cap the cap Cell divisions at the apical Cell divisions at the apical

meristem cause the root to meristem cause the root to lengthenlengthen

Farther up, cells Farther up, cells differentiate and maturedifferentiate and mature

Figure 29.16.a

Page 502

Internal Structure of a RootInternal Structure of a Root

Outermost layer is epidermisOutermost layer is epidermis

Root cortex is beneath the epidermisRoot cortex is beneath the epidermis

Endodermis, then pericycle surround Endodermis, then pericycle surround

the vascular cylinderthe vascular cylinder

In some plants, there is a central pithIn some plants, there is a central pith

primary xylem

primary phloem

epidermis

VASCULAR CYLINDER

cortex

pith

Fig. 29-17, p.503

Fig. 29-18, p.503

Formation of a lateral root

- Originates in the pericycle and grows out through the cortex and epidermis

Fig. 29-18a, p.503

Fig. 29-18b, p.503

Fig. 29-18c, p.503

Function of EndodermisFunction of Endodermis

Ring of cells surrounds vascular cylinderRing of cells surrounds vascular cylinder

Cell walls are waterproof Cell walls are waterproof

Water can only enter vascular cylinder by Water can only enter vascular cylinder by

moving through endodermal cellsmoving through endodermal cells

Allows plant to control inward flowAllows plant to control inward flow

Root Hairs and Lateral RootsRoot Hairs and Lateral Roots

Both increase the surface area Both increase the surface area

of a root systemof a root system

Root hairs are tiny extensions Root hairs are tiny extensions

of epidermal cellsof epidermal cells

Lateral roots arise from the Lateral roots arise from the

pericycle and must push pericycle and must push

through the cortex and through the cortex and

epidermis to reach the soilepidermis to reach the soil

newlateralroot

Fig. 29-19, p.503

Fig. 29-19a, p.503

Fig. 29-19b, p.503

Secondary GrowthSecondary Growth

Occurs in all gymnosperms, some Occurs in all gymnosperms, some

monocots, and many dicotsmonocots, and many dicots

A ring of vascular cambium produces A ring of vascular cambium produces

secondary xylem and phloemsecondary xylem and phloem

Wood is the accumulation of these Wood is the accumulation of these

secondary tissues, especially xylem secondary tissues, especially xylem

What Happens at What Happens at Vascular Cambium?Vascular Cambium?

Fusiform initials give rise to Fusiform initials give rise to secondary xylem and phloemsecondary xylem and phloem

Ray initials give rise to horizontal Ray initials give rise to horizontal rays of parenchyma rays of parenchyma

Fig. 29-20, p.504

cork cambium vascular cambium

thickening

Fig. 29-20a, p.504

primary xylem

primary phloem

VASCULAR CAMBIUM

VASCULAR CAMBIUM

secondary xylem

secondary phloem

stem surface

Fig. 29-20b, p.504

outer surface of stem root

divisiondivision

One of the cells vascular cambium at the start of secondary growth.

One of the two daughter cells differentiates into a xylem cell (coded blue), and the other remains meristatic.

One of the two daughter cells differentiates into a phloem cell (coded pink), and the other remains meristatic.

The same pattern of cell division and differentiation into xylem and phloem cells continues through the growing season.

Fig. 29-20c, p.504

Secondary GrowthSecondary Growth

Figure 29.20.cPage 504

Ongoing cell divisions enlarge the inner core of secondary xylem and displace vascular cambium toward the stem

Secondary growth

Secondary GrowthSecondary Growth

Formation of BarkFormation of Bark

All tissues outside vascular cambiumAll tissues outside vascular cambium PeridermPeriderm

CorkCork New parenchymaNew parenchyma Cork cambium Cork cambium

Secondary phloemSecondary phloem

Fig. 29-23, p.506

A Coast A Coast RedwoodRedwood

periderm (includes cork cambium, cork, new parenchyma)

secondary phloem

BARK

vascular cambium

HEARTWOOD SAPWOOD

Fig. 29-24a, p.507

Annual RingsAnnual Rings

Concentric rings of secondary xylemConcentric rings of secondary xylem Alternating bands of early and late woodAlternating bands of early and late wood Early woodEarly wood

Xylem cells with large diameter, thin wallsXylem cells with large diameter, thin walls Late woodLate wood

Xylem cells with smaller diameter, thicker Xylem cells with smaller diameter, thicker walls walls

Fig. 29-25a, p.507

year 1 2 3

Fig. 29-25b, p.507

1587–1589 1606–1612

Fig. 29-27c, p.509

Annual RingsAnnual Rings Narrow annual rings mark severe drought Narrow annual rings mark severe drought

yearsyears

Types of WoodTypes of Wood

Hardwood (oak, hickory)Hardwood (oak, hickory) Dicot woodDicot wood Xylem composed of vessels, tracheids, and Xylem composed of vessels, tracheids, and

fibersfibers Softwood (pine, redwood)Softwood (pine, redwood)

Gymnosperm woodGymnosperm wood Xylem composed mostly of tracheidsXylem composed mostly of tracheids Grows more quicklyGrows more quickly