Lesson 12 bio101 (c)Dr. Evangelista

Secretorystructures  Secretion–thereleaseofsubstancesthathaveaspecialphysiologicfunction(enzymes,hormones)

 Excretion‐separationofproductseliminatedfrommetabolism

 Secretionisusedtoincludeexcretion: roleofmanyofthesesubstancesisnotknown theymaybefoundinthesamecontainer Secretionmayremaininthecellproducingitasdroplets,bewalledofffromthecytoplasmorleavethecell

Typesofsecretorystructures  Externalsecretorystructures

 A.Trichomeandglands B.Nectaries C.Osmophors D.Hydathodes

 Internalsecretorystructures A.Secretorycells B.Secretoryspaces C.Laticifers

Typesofsecretorystructures  Externalsecretorystructures

 A.Trichomeandglands B.Nectaries C.Osmophors D.Hydathodes

 Internalsecretorystructures A.Secretorycells B.Secretoryspaces C.Laticifers

Trichomesandglands  trichomessimplerthanglandsalthoughnosharpdistinctionexistsbetweenglandularhairsandglands  Trichomes

  Containsanti‐herbivoresecretions

 Glands  Saltglands‐mechanismfortheplanttogetridofexcesssaltabsorbedfromtheenvironment  Functionofplantslivinginsaltmarshesandsaltinfiltratedsoilsincoastalmarineareas

  Glandsofinsectivorousplants‐secretedigestivejuices

GlandularhairofUrticadioica(stingingnettle)

‐Uponcontactwithananimal,thetipbreaksoffreleasingthetoxicsubstancesinthecellasitpenetratestheskin.

‐Reportedtocontainahistamineandanacetylcholine

SaltglandofTamarixaphylla

Note that the gland, whichconsists of two basalcollecting cells and foursecretory cells, is sunken inthe epidermis. Salt istransferred symplasticallyfromtheleafmesophyllintocollectingcellsandsecretorycells and apoplasticallythroughthewalllabyrinthtotheexterior

 Structureofsecretorycells Havedenseprotoplast Largenucleus

 Mechanismsforrelease 1.Mayreleasesecretioninbetweenwallandcuticle

 A.Eventuallycuticlebursts(mayregeneratecuticleordryupafterexcretion)

 B.Ornotatallbutindividualcellsareseveredafterreleaseofsecretion

 2.Specialmechanism(tipbreaksoffandcontentse.g.histamineescapeintowound)

Glandulartrichome

GlandularhairofUrticadioica(stingingnettle)

‐Uponcontactwithananimal,thetipbreaksoffreleasingthetoxicsubstancesinthecellasitpenetratestheskin.

‐Reportedtocontainahistamineandanacetylcholine

Nectaries  Mayoccuronflowers(floralnectaries)orvegetativeparts(extrafloralnectaries) Secretorytissue

 restrictedtotheepidermallayerormayincludesubsurfacelayers

 havedensecytoplasm maybepapillate arecloselypacked  havethinwalls

Nectaries Sugarsofnectariesderivedfromphloem

 Nectarexcretedthrough

 cellwallandrupturedcuticle

  orthroughstomates(thatarenotabletocloseandopen)

Osmophors  scentoftheflowersproducedbyessentialoils

 originatesfromepidermisofperianthorfromosmophors(specialglands)

 osmophorsfoundinAristolochiaceae,Araceaeetc.

  floralpartsdifferentiatedasosmophorsmayassumetheformofflaps,brushesorcilia

 maybedistinguishedbyusingneutralred

Methodtolocateosmophors

Secretorytissueofosmophors

Emission of volatilesecretion is of shortdurationand isassociatedwith utilization of largeamounts of s torageproducts

Hydathodes Astructurethatdischargewaterfromtheinterioroftheleaftothesurface watercontainsdissolvedsalts,sugarsandotherorganicsubstances

 Eliminateswaterthroughtheterminaltracheid  incontactwithepithem mayhavenoepithemandwatermovesthroughordinarymesophyll

Guttation,theexudationofwaterdropletsOccurswhenwaterabsorption>lossofwater

hydathode

Internalsecretorystructures  Secretorycells

 Crystal‐containingcellsmaydieafterdepositionofthecrystalormaybeseparatedfromlivingpartoftheprotoplast

 Secretoryspaces

 Intheformofspacesorcavitiesformedbyschizogeny,lysigenyortheircombination

 Epithelialcellsofresincanals

 Lysigenousspace

Secretorycells

SecretorycellsA.CellscontainingtanninsB.Oilidioblast

SecretoryspacesA‐D.SchizogenouscavitiesE.Lysigenouscavity

Internalsecretorystructures  Laticifers

 DerivedfromthewordlatexmeaningjuiceinLatin

 Becauseofthemilkyappearanceofthelatex,itissometimescalledlactiferouscellsorvesselsfromtheLatinwordformilk,lac

 Laticifers Accordingtoorigin:

  1.Simplelaticifer–derivedfromasinglecell 2.Compoundlaticifer–derivedfromunionofcells

 Accordingtostructure:  1.Articulatedlaticifer‐(laticiferousvessel)

 compoundinoriginconsistschainsofcells  endwallsmayremain,becomeperforatedorarecompletelyremoved

 Laticifers Accordingtostructure:

  1.Types:

 Articulatednonanastomosing‐compoundtubesnotconnectedwitheachotherlaterally(Ipomoea,Convolvulus,Achrassapota,Allium,Musa)

 Articulatedanastomosing‐cellchainsconnectedwitheachotherlaterally(Hevea,Lactuca,Caricapapaya,Manihot)

LaticifersinAlliumsativum

laticifers

 Laticifers Accordingtostructure:

 Nonarticulatedlaticifer‐(laticiferouscell)   simpleinorigin   throughcontinuedgrowthdevelopsintoatube‐likestructure

 Types:   Nonarticulatedunbranched–developmoreorlessstraighttubes(Vinca,Urtica,Cannabis)

  Nonarticulatedbranched–eachcellformsbranchrepeatedlyforminganimmensesystemoftubes(Nerium,Ficus,Euphorbia)

 Laticifers Compositionandphysicalstateoflatex Liquidmatrixwithminuteorganicsuspension

 Matrixcontain:carbohydrates,organicacids,salts,alkaloids,sterols,fats,tannins,andmucilages

 Thedispersedparticles:terpenesi.e.,essentialoils,balsams,resins,camphors,carotenoidsandrubber

 Latexmaybeclearormilky

 Flowoflatexinwhencutopenisapressureflow

CompositionoflaticifersLatexwithnumerousvesicles;containpolyterpenesandothercompounds

 Laticifers Cytology

 Withlivingprotoplastretainingnucleusatfunctionalmaturity

 Cytoplasmalongtheperipherysurroundingthevacuolarsap

  Innonarticulatedformofmanyplants,thenucleiundergodivisionsresultinginamultinucleatecoenocyticcondition

 Laticifers Cytology

  ifmultinucleateinarticulatedforms,itisduetofusionofprotoplasts

  thelatexparticlesareformedinthecytoplasm

  thetonoplastbreaksdowninmaturelaticifers;thelatexparticlesescapeintothevacuolarsapwhichbecomepartofthelatex

 Laticifers Structureofthewall

 nonlignifiedandplastic

 Development Nonarticulatedlaticifers  A.Branched

o Arisewhenthecotyledonsareinitiatedintheformofrelativelyfewprimordia

o growconcomitantlywiththeplantintobranchedsystemspermeatingthewholeplantbody

Nonarticulatedlaticiferofneriumoleander(development)

 Laticifers Development

 Nonarticulatedlaticifers   B.Unbranched–primordiaseenindevelopingshoot(Vinca,Cannabis)orintheshootandrootandnewprimordiaariserepeatedlybeneaththeapicalmeristembyacombinationofintrusivegrowthandsymplasticgrowth

 Laticifers Development

 Articulatedlaticifers   A.anastomosing

o  developsintoextensivetube‐likestructures,byconstantadditionofnewprimordiatotheexistingones

o  inthehypocotylsandthecotyledonsoftheembryointhematureseed

o  endwallsofprimordiaareintactbutduringgerminationbreakdownandthecellrowsareconvertedintovessels

 Laticifers Development

  Articulatedlaticifers   A.anastomosing

o  thevesselsareextendedbydifferentiationoffurthermeristematiccellsintolaticiferouselementsinacropetaldirection

o  wherethevesselsliesidebyside,partsofthecommonwallbecomeresorbed;iftheyarefurtherapart,theinterveningcellsmaybecomechangedintolaticiferouscellswithresorptionofcommonwalls;someoftheanastomosesmayendupblindly

o  inthesecondaryphloemmaydevelopfromderivativesoffusiforminitials

 Laticifers Development

 Articulatedlaticifers

  B.nonanastomosing

o  thedevelopmentofnonanastomosingkindissimilartoanastomosinglaticifers,exceptthatnolateralconnectionsareestablishedamongthevarioustubes

Articulatedlaticiferdevelopment

 Laticifers Arrangementintheplant

  frequentlydistributedgenerallythroughtheplant

  sometimesarerestrictedtocertaintissues   mostcommonlythephloem   mayoccuralsointhexylem(Caricaceae)   cortex(Musa)   pericycle   mesophyll

Arrangementoflaticifersintheplant

 Laticifers Possiblefunction Vitalsapvesselslikebloodvesselsofanimals

 Takepartinthetranslocationofassimilates

 Takepartinthestorageoffoodmaterials

 Theyformanexcretorysystem

 Protectionasthelatexmayplayarolein:   coveringwounds   asdefenseagainstherbivoresandmicroorganisms