Plant StructurePlant Structure

An overviewAn overview

Plant CellsPlant Cells

Cell WallsCell Walls

Primary Primary

SecondarySecondary

Middle lamellaMiddle lamella

PlasmodesmataPlasmodesmata

Plant BodyPlant Body

Root SystemRoot System UndergroundUnderground

Shoot systemShoot system LeavesLeaves StemsStems FlowersFlowers

Plant tissuesPlant tissues

Simple tissues vs. complex tissuesSimple tissues vs. complex tissues

Vascular plants have 3 tissue systems:Vascular plants have 3 tissue systems: GroundGround VascularVascular DermalDermal

Ground tissueGround tissue

Makes up most of plant bodyMakes up most of plant body

Variety of functions:Variety of functions: PhotosynthesisPhotosynthesis Storage of materialsStorage of materials SupportSupport

Composed of 3 simple tissuesComposed of 3 simple tissues Based on composition of cell wallBased on composition of cell wall

Ground tissue, cont.Ground tissue, cont.

Parenchyma tissueParenchyma tissue Most common type of cell and tissueMost common type of cell and tissue Thin primary cell wallsThin primary cell walls Edible parts of plantsEdible parts of plants Functions: photosynthesis, secretion, Functions: photosynthesis, secretion,

storagestorage Metabolically activeMetabolically active Have ability to differentiateHave ability to differentiate

Ground tissue, cont.Ground tissue, cont. Collenchyma cellsCollenchyma cells

Provides support in herbaceous plantsProvides support in herbaceous plants Primary cell wall is unevenly thickPrimary cell wall is unevenly thick

Thickest at cornersThickest at corners

Alive at maturityAlive at maturity

Schlerenchyma cellsSchlerenchyma cells Thick secondary cell wallsThick secondary cell walls Strength and supportStrength and support Often dead at maturityOften dead at maturity

Vascular TissueVascular Tissue

Embedded in ground tissueEmbedded in ground tissue

Transports materialTransports material

Made of 2 complex tissuesMade of 2 complex tissues XylemXylem PhloemPhloem

XylemXylem

Conducts waterConducts water

Provides supportProvides support

Made of 4 cell types:Made of 4 cell types: FibersFibers Xylem parenchymaXylem parenchyma TracheidsTracheids Vessel elementsVessel elements

Conducting Cells in Conducting Cells in XylemXylem TracheidsTracheids

Dead at maturityDead at maturity HollowHollow Long, taperingLong, tapering PitsPits

Vessel elementsVessel elements Dead at maturityDead at maturity Larger diameterLarger diameter End walls perforated or absentEnd walls perforated or absent Pits in side wallPits in side wall

PhloemPhloem

Conducts carbohydrates throughout the plantConducts carbohydrates throughout the plant

Provides supportProvides support

Composed of 4 cell types:Composed of 4 cell types: Phloem parenchymaPhloem parenchyma FibersFibers Sieve tube elementsSieve tube elements Companion cellsCompanion cells

Conducting Cells in Conducting Cells in PhloemPhloem

Sieve tube elementsSieve tube elements Alive at maturityAlive at maturity

Lack many organellesLack many organelles

Sieve plate at endSieve plate at end Carry dissolved sugarsCarry dissolved sugars

Companion cellsCompanion cells Connected to sieve tube elements by Connected to sieve tube elements by

plasmodesmataplasmodesmata Assist in functioning of sieve tube elementsAssist in functioning of sieve tube elements

Dermal tissueDermal tissue

Covers and protects the plantCovers and protects the plant

Composed of 2 complex tissuesComposed of 2 complex tissues EpidermisEpidermis PeridermPeriderm

EpidermisEpidermis

Primarily unspecialized epidermal cellsPrimarily unspecialized epidermal cells TransparentTransparent Secrete cuticleSecrete cuticle

Specialized guard cellsSpecialized guard cells Open and close stomataOpen and close stomata

TrichomesTrichomes Outgrowths, hairOutgrowths, hair

PeridermPeriderm

Replaces epidermis in woody plantsReplaces epidermis in woody plants

Composed of:Composed of: Cork parenchymaCork parenchyma Cork cellCork cell

Dead at maturityDead at maturity Walls coated with waxy suberinWalls coated with waxy suberin

Periderm forms outer barkPeriderm forms outer bark

Plant GrowthPlant Growth

Plant growth involves:Plant growth involves: Cell divisionCell division

MitosisMitosis Cytokinesis – cell plate divides new cellsCytokinesis – cell plate divides new cells

Cell elongationCell elongation Cytoplasm growsCytoplasm grows Vacuole increases in sizeVacuole increases in size

Cell differentiation - specializationCell differentiation - specialization

GrowthGrowth

IndeterminateIndeterminate Continues throughout plant’s lifeContinues throughout plant’s life

DeterminateDeterminate Plant part reaches a certain size Plant part reaches a certain size

then stopsthen stops

Primary vs. Secondary Primary vs. Secondary Primary – lengthPrimary – length Secondary - girthSecondary - girth

MeristemsMeristems

Only locations where plant cells divideOnly locations where plant cells divide

Undifferentiated cellsUndifferentiated cells

Primary function is mitosisPrimary function is mitosis

Primary GrowthPrimary Growth

Occurs at apical meristemsOccurs at apical meristems Tips of roots and shootsTips of roots and shoots

In roots, meristem is directly behind root capIn roots, meristem is directly behind root cap

Shoot apical meristem formsShoot apical meristem forms Leaf primordiaLeaf primordia Bud primordiaBud primordia

Further away cells move from apical meristems, begin Further away cells move from apical meristems, begin to differentiateto differentiate

Secondary GrowthSecondary Growth Occurs in trees and shrubsOccurs in trees and shrubs

Due to lateral meristemsDue to lateral meristems

2 lateral meristems2 lateral meristems Vascular cambiumVascular cambium – located between wood – located between wood

and bark - forms secondary xylem and and bark - forms secondary xylem and secondary phloemsecondary phloem

Cork cambiumCork cambium – in outer bark – forms cork – in outer bark – forms cork cells and cork parenchymacells and cork parenchyma

BarkBark Outermost covering of woody stems and Outermost covering of woody stems and

rootsroots

All plant tissues located outside the All plant tissues located outside the vascular cambiumvascular cambium

2 regions:2 regions: Living inner bark Living inner bark secondary phloem secondary phloem Dead outer bark Dead outer bark periderm periderm