Plant StructuresPlant StructuresRoots, Stems, and LeavesRoots, Stems, and Leaves

Chapter 23Chapter 23

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants Plants are as successful Plants are as successful

if not more successful if not more successful than animalsthan animals

Seed plants have three Seed plants have three main structures:main structures: RootsRoots StemsStems LeavesLeaves

Linked together by Linked together by various meansvarious means

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants RootsRoots

Absorbs water and Absorbs water and nutrientsnutrients

Anchor plant to the Anchor plant to the groundground

Hold soil in place and Hold soil in place and prevent erosionprevent erosion

Protect from soil bacteriaProtect from soil bacteria Transport water and Transport water and

nutrientsnutrients Provide upright supportProvide upright support

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants StemsStems

Support for the plant Support for the plant bodybody

Carries nutrients Carries nutrients throughout plantthroughout plant

Defense system to Defense system to protect against predators protect against predators and infectionand infection

Few millimeters to 100 Few millimeters to 100 metersmeters

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants LeavesLeaves

Main photosynthetic Main photosynthetic systemssystems

Suseptable to extreme Suseptable to extreme dryingdrying

Sight of oxygen/carbon Sight of oxygen/carbon dioxide intake and dioxide intake and releaserelease

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants Plant tissue Plant tissue

systemssystems Exist within the Exist within the

root, stems, and root, stems, and leavesleaves Dermal tissueDermal tissue Vascular tissueVascular tissue Ground tissueGround tissue

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants Dermal TissueDermal Tissue

Outer covering Outer covering Single layer of cellsSingle layer of cells CuticleCuticle – waxy coating – waxy coating

TrichomesTrichomes – – Spiny Spiny projections on the leafprojections on the leaf

Roots have dermal tissueRoots have dermal tissue Root hairsRoot hairs

Guard CellsGuard Cells

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants Vascular TissueVascular Tissue

Transport SystemTransport System SubsystemsSubsystems

XylemXylem PhloemPhloem

Subsystems are used to carry fluids Subsystems are used to carry fluids throughout plantthroughout plant

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants XylemXylem

Two typesTwo types Seed plantsSeed plants AngiospermsAngiosperms

Tracheid Tracheid – long narrow – long narrow cellscells

Walls are connected to Walls are connected to neighboring cellsneighboring cells

Will eventually dieWill eventually die Vessel ElementVessel Element – wider – wider

that trachiedsthat trachieds

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants PhloemPhloem

Sieve Tube ElementsSieve Tube Elements Cells arranged end to endCells arranged end to end Pump sugars and other foodsPump sugars and other foods

Companion CellsCompanion Cells Surround sieve tube elementsSurround sieve tube elements Support phloem cellsSupport phloem cells

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants Ground TissueGround Tissue

Cells between dermal Cells between dermal and vascular tissueand vascular tissue

ParenchymaParenchyma Thin cell walls, large Thin cell walls, large

vacuoulesvacuoules CollenchymaCollenchyma

Strong, flexible cell wallsStrong, flexible cell walls SclerenchymaSclerenchyma

Extremely thick, rigid cell Extremely thick, rigid cell wallswalls

23-1 Specialized Tissues in Plants23-1 Specialized Tissues in Plants Plant GrowthPlant Growth

MeristemsMeristems – tissues – tissues responsible for growth responsible for growth

Undifferentiated cellsUndifferentiated cells Apical MeristemApical Meristem

Produce growth increased Produce growth increased lengthlength

DifferentiationDifferentiation Cells will assume roles in Cells will assume roles in

the plantthe plant Flower DevelopmentFlower Development

Starts in the meristemStarts in the meristem

23-2 Roots23-2 Roots

Types of RootsTypes of Roots TaprootsTaproots

Found in dicotsFound in dicots Long, thick rootLong, thick root Hickory and oak treesHickory and oak trees

Fibrous rootsFibrous roots Found in monocotsFound in monocots No single root larger than any otherNo single root larger than any other Many thin rootsMany thin roots

23-2 Roots23-2 Roots Root StructureRoot Structure

Outside layerOutside layer EpidermisEpidermis

Root hairsRoot hairs CortexCortex

Central cylinder – Central cylinder – vascular systemvascular system

Root Cap – cellular Root Cap – cellular productionproduction

Key role in Key role in water/mineral transportwater/mineral transport

23-2 Roots23-2 Roots Root FunctionsRoot Functions

Anchor plantAnchor plant Absorb waterAbsorb water Absorb nutrientsAbsorb nutrients

23-2 Roots23-2 Roots Plant Nutrient UptakePlant Nutrient Uptake

Soil type determines Soil type determines plant typeplant type

Plant requirementsPlant requirements Oxygen, COOxygen, CO2 2 NitrogenNitrogen PhosphorusPhosphorus PostassiumPostassium MagnesiumMagnesium CalciumCalcium Trace elementsTrace elements

23-2 Roots23-2 Roots Active Transport in Active Transport in

PlantsPlants Root hairs use ATP Root hairs use ATP

Pump minerals from soilPump minerals from soil Causes water molecules to Causes water molecules to

follow by osmosisfollow by osmosis Vascular CylinderVascular Cylinder

Casparian Strip – water Casparian Strip – water retentionretention

Root PressureRoot Pressure Forces water up into the Forces water up into the

plantplant

23-3 Stems23-3 Stems Stem StructureStem Structure

Produce leaves, Produce leaves, branches, and flowersbranches, and flowers

Hold leaves upHold leaves up Transport substance Transport substance

between roots and leavesbetween roots and leaves Essential part of Essential part of

transport systemtransport system Function in storage and Function in storage and

photosynthesisphotosynthesis

23-3 Stems23-3 Stems Xylem and phloem – major Xylem and phloem – major

tubule systemstubule systems Transport water and nutrientsTransport water and nutrients

Composed of three tissue Composed of three tissue layerslayers

Contain Contain nodesnodes – attachment – attachment for leaves for leaves

InternodesInternodes – regions – regions between the nodesbetween the nodes

BudsBuds – undeveloped tissue – undeveloped tissue

23-3 Stems23-3 Stems Stem TypesStem Types

MonocotMonocot – vascular – vascular bundles are scattered bundles are scattered throughoutthroughout

Distinct epidermisDistinct epidermis DicotDicot – vascular tissue – vascular tissue

arranged in a cylinderarranged in a cylinder PithPith – parenchyma cells – parenchyma cells

inside the ringinside the ring

23-3 Stems23-3 Stems Stem GrowthStem Growth

Primary growth – new Primary growth – new cells produced at the root cells produced at the root tips and shootstips and shoots

Increases the lengthIncreases the length Secondary growth – Secondary growth –

increase in stem widthincrease in stem width Vascular cambium – Vascular cambium –

produces tissue and produces tissue and increases thicknessincreases thickness

Cork cambium – produces Cork cambium – produces outer covering of stemsouter covering of stems

23-3 Stems23-3 Stems Formation of Vascular Formation of Vascular

CambiumCambium Xylem and phloem Xylem and phloem

bundles present intiallybundles present intially Secondary growth Secondary growth

initiates production of a initiates production of a thin layerthin layer

The vascular cambium The vascular cambium dividesdivides

Produces new xylem and Produces new xylem and phloemphloem

23-3 Stems23-3 Stems Formation of woodFormation of wood

Wood – layers of exlemWood – layers of exlem Produced year after yearProduced year after year Results from the older xylem not conducting water – Results from the older xylem not conducting water – heartwoodheartwood Becomes darker with ageBecomes darker with age SapwoodSapwood – surrounds heartwood – surrounds heartwood

23-3 Roots23-3 Roots Formation of BarkFormation of Bark

All the tissues outside All the tissues outside the vascular cambiumthe vascular cambium

Consists of outermost Consists of outermost layers of dead corklayers of dead cork

Water proofWater proof

23-4 Leaves23-4 Leaves Main sight of Main sight of

photosynthesisphotosynthesis Consist of:Consist of:

Blade – thin flattened Blade – thin flattened sectionsection

Petiole – stalk that Petiole – stalk that attaches stem to bladeattaches stem to blade

Covered by epidermis Covered by epidermis and cuticleand cuticle Create water proof Create water proof

barrierbarrier

23-4 Leaves23-4 Leaves Leaf FunctionsLeaf Functions

Photosynthesis – occurs Photosynthesis – occurs in the mesophyllin the mesophyll

Palisade mesophyll – Palisade mesophyll – absorb lightabsorb light

Spongy mesophyll – Spongy mesophyll – beneath palisede levelbeneath palisede level

Stomata – pores in the Stomata – pores in the underside of the leafunderside of the leaf

Guard CellsGuard Cells – Surround – Surround the stomatathe stomata

23-4 Leaves23-4 Leaves TranspirationTranspiration

Loss of water through its leavesLoss of water through its leaves Replaced by water drawn into the leafReplaced by water drawn into the leaf

23-4 Leaves23-4 Leaves Gas ExchangeGas Exchange

Take in COTake in CO2 2 and release and release OO22

Can also do the opposite Can also do the opposite – How?– How?

Gas exchange takes place Gas exchange takes place at the stomataat the stomata

Not open all the timeNot open all the time Stomata is controlled by Stomata is controlled by

water pressure in guard water pressure in guard cellscells

23-5 Transport in Plants23-5 Transport in Plants Water TransportWater Transport

Active transport and root Active transport and root pressurepressure

Cause water to move from Cause water to move from soil to rootssoil to roots

Capillary actionCapillary action Combined with active Combined with active

transport and root transport and root pressure, moves materials pressure, moves materials throughout the plantthroughout the plant

23-5 Transport in Plants23-5 Transport in Plants Capillary TransportCapillary Transport

Capillary transport Capillary transport results from both results from both cohesive and adhesive cohesive and adhesive forcesforces

Water molecules Water molecules attracted to one anotherattracted to one another

Water is also attracted to Water is also attracted to the xylem tubes in the the xylem tubes in the plantplant

Causes water to move Causes water to move from roots to the stem from roots to the stem and upwardand upward

23-5 Transport in Plants23-5 Transport in Plants TranspirationTranspiration

Evaporation is the major Evaporation is the major moving forcemoving force

As water is lost, osmotic As water is lost, osmotic pressure moves water out pressure moves water out of vascular tissueof vascular tissue

This pulls water up from This pulls water up from the stem to the leavesthe stem to the leaves

Affected by heat, Affected by heat, humidity, and windhumidity, and wind

23-5 Transport in Plants23-5 Transport in Plants Controlling Controlling

TranspirationTranspiration Open the stomata – Open the stomata –

increase water lossincrease water loss Close the stomata – Close the stomata –

decrease water lossdecrease water loss

23-5 Transport in Plants23-5 Transport in Plants Transpiration and Transpiration and

WiltingWilting Osmotic pressure – Osmotic pressure –

keeps plants semi-rigidkeeps plants semi-rigid Wilting is a result of Wilting is a result of

high transpiration rateshigh transpiration rates Loss of water causes a Loss of water causes a

drop in osmotic pressuredrop in osmotic pressure Loss of rigidityLoss of rigidity Conserves waterConserves water

23-5 Transport in Plants23-5 Transport in Plants Nutrient TransportNutrient Transport

Most nutrients are Most nutrients are pushedpushed through plant through plant

Nutrient movement takes Nutrient movement takes place in phloemplace in phloem

Source to SinkSource to Sink Source – any cell that Source – any cell that

produces sugarsproduces sugars Sink – any cell where Sink – any cell where

sugars are usedsugars are used Pressure-flow Pressure-flow

HypothesisHypothesis