Composedoflivingcells Cellswiththinwalls Polyhedralshapeofcells Fundamentalorgroundtissueinwhichothertissuesareembedded

 Foundationoftheplant(reproductivecellsandapicalmeristemsareparenchymaticinnature)

  Involvedinwoundhealing

 Precursorofothertissues(structureofprimitiveplants)

 Developmentallyundifferentiated

 Unspecializedphysiologically

 Storageparenchyma withleucoplastids conspicuouslyvacuolated–withwater,pigment,tannins,crystals,amides,proteinsandsugar

 Aerenchyma

  withlargeintercellularspaces

  forbuoyancyandaeration

  thestructureprovidesstrengthwiththeleastpossibleamountoftissue

CHLORENCHYMA

  withhighcontentinchlorophyll

  livingtissue,madeupofelongatedcells

 withthickprimarynonlignifiedwalls

  thickeningsdepositedunevenly

  forsupport

 mayhavechloroplastids

 mayresumemeristematicactivity

 Supportingtissue ofgrowingorgans  matureherbaceousorgans

 absentinmanystemsandleavesofmonocotsthatearlydevelopsclerenchyma

 mayoccurinaerialroots

 occursinperipheralpositioninstemsandleaves

  ‐inoneorbothsidesoftheleafvein

 angular–maindepositsofwallmaterialinthecorners

 lamellar–thickeningschieflyontangentialwalls

 lacunar–withintercellularspaces;developmentofthickeningsonthewallsfacingtheintercellularspaces

A

B

C

 Mechanicaltissueadaptedforsupportofgrowingorgans  ‐withthickwallsandclosepackingmakeitastrongtissue

  ‐cansimultaneouslyincreaseinsurfaceareaandthickness

  ‐combinestensilestrengthwithflexibilityandplasticity

 Collenchymamaydeveloplignifiedsecondarywalls‐becomessclerenchyma

 Thick‐walledcells

 Oftenlignified

 Principalfunctionismechanical

 Withhard,elasticsecondarywalls

 Typicallywithoutlivingprotoplast

 Mayretaintheirprotoplast,thus,arenotsharplydelimitedfromparenchyma

 Fibers‐longcells

 Sclereids‐areshortcells sclereidsmaybeshorttolong

 Distinguishedbytypeofpitting

DA

C

DB

  xylemandphloem–derivedfromprocambiumorvascularcambium

  extraxylaryfibersotherthanphloem–groundmeristem

 Cyperaceaefibersofepidermalorigin

  PrimaryfibersarelongerthansecondaryfibersI

Occurrenceandarrangementinplant Seedcoat–hardnessandstrength Scale–epidermis Fleshoffruits(Pyrus)  Inthebreaksoftheperivascularregion Shellsofnuts Endocarpofstonefruits

 Brachysclereids–stonecells,short,roughlyisodiametric,resemblingparenchymainshape

 Macrosclereids–elongated,rod‐likecells(formingpalisade‐likeepidermallayerofleguminousseeds)

 Osteosclereids–bone‐shapedsclereidse.g.seedcoat

 Astrosclereid–star‐shapede.g.leavesofdicot

 Filiformsclereid–long,slendercells,resemblingfiberse.g.oliveleafofspongyandpalisade

 Trichosclereid–branched,thin‐walledsclereidsresemblingplanthairse.g.airrootsofMonstera

 Varyinthicknessandaretypicallylignified

 Withprominentsimplepits

 Mayretainprotoplastorbecomedead

Origin

  Throughbelatedsclerosisofordinaryparenchymacells

  Directlyfromcellsthatareearlyindividualizedassclereidprimordial

 Withinthevasculartissues–sclereidsoriginatefromprocambiumorcambium

  Stonecellsincorkcomesfromthephellogen

 Macrosclereidsoftheseedcoatareprotodermalinorigin

 Maygrowbycombinationofsymplasticandapicalintrusivegrowth