Plant StructuresPlant StructuresStemsStems

Horticulture I 2014Horticulture I 2014

Specialized Tissues in PlantsSpecialized 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

Specialized Tissues in PlantsSpecialized 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

Specialized Tissues in PlantsSpecialized 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

Specialized Tissues in PlantsSpecialized 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

Specialized Tissues in PlantsSpecialized 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

Specialized Tissues in PlantsSpecialized 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

Specialized Tissues in PlantsSpecialized 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

Specialized Tissues in PlantsSpecialized 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

Specialized Tissues in PlantsSpecialized 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

StemsStems

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

StemsStems

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

StemsStems

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

StemsStems

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

StemsStems

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

StemsStems

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

StemsStems

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