lesson 12 bio101 (c)dr. evangelista
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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