Translocation In Phloem

1. FergussonCollegePune
Name:-pankajBaluMore
Class:-T.Y.BSc
Rollno.:-213705
Subject:-plantphysiologyandbiochemistry
Subjectcode:-BOT3601
Topic:-TranslocationinPhloem

2. IntroductionofPhloem
‘’Itisthefoodconducting tissueofvascularparts’’
Itis madefourComponents
1. Sieveelements
2. Companioncells
3. PhloemParenchyma
4. PhloemFiber

3. Sieveelements:-thecellsofthephloemthattranslocation
sugarandothersorganicmaterial throughouttheplantare
calledsieveelements
Companion Cells:-itisattachto sieveelement through
numerouschannelsknownasplasmodesmata ,itprovide
energytosieveelementsinfromofATP,Sieveelementdoes
nothavemoreorganels,sieveelementslivebycompanioncells
theyprovideenergytosieveelements.
1. SecondFunctionofcompanioncellsisPhloemLoadingand
Unloading,companioncellsloadsugarsTo Sieveelements

4. PhloemParenchyma:-itworksasfood
storageandTransferofsugarfrommesophyll
cells.tocompanioncellsandcompanioncells
loadssugarto sieveelements.
PhloemFiber:-itprovidemechanical
supporttoPhloem

5. PhloemTranslocation
 Themovementofphloemsap overlong distancesthroughphloemisknownasphloem
Translocation.
 Photoassimilatestranslocated fromsiteofphotosynthesis(matureleaves)totheareaof
growthandstorage.The cells ofthephloemthroughwhich photoassimilatesmove
throughouttheplantsare called SieveElements.
 Sieveelementsincludesbothsieve tubeelementsofangiospermsandlessspecialized Sieve
cellsofGymnosperms.
 Sieve tubeelementsofangiospermsare elongatedlivingcellswithsieve platesandforms
openchannels.

6.  Thesievetubeofmostangiosperms(alldicotsandmanymonocots)also
containsphloemprotein.
 P-proteinfunctionsinsealingofdamaged sieve tubeelements toprevent
lossofsap.
 Ingymnospermssieve elementsarecalled sieve cells.Insieve thereisno
sieve plate
1. Alongwithsieve tubeelementsthereisnon-conductingcells called
companioncellswhichisconnectedtosieve tubebynumerouschannels,
called plasmodesmata.companioncellsarecalled albuminouscellsin
gymnosperms.

7. 2.Companion cell plays a role in the transport of photoassimilates from
producing cell in mature leaves to the sieve elements in the minor veins of the
leaf. Companion cells also functions as nurse cells and supply energy as ATP to
sieve tube elements.
Companioncells
Thereare3typesofCompanioncellsintheminorveinsofmature
exportingleaves.
 OrdinaryCompanioncells.:-
1. Havesmoothwallswithfeworno.plasmodesmataconnectiontocells
otherthansievetube
2. Functioninapoplasticstransportofsugarfrommesophyllcellsto
sieveelements(loading)and apoplasticsunloadinginplants.

8. Transfercells
1. Arelikeordinarycompanioncellsbuthavefingerlike foldedwalls
whichincreasesurfaceareaoftransfercells.
2. Itfunctionsinapoplasticstransportofsugarfrommesophyllcellsto
sieve elements(loading)andapoplasticunloadinginplants.
IntermediaryCompanioncells
1. Havesmoothwallswithnumerousplasmodesmataconnectingthem
toothercells.
2. Functionin thesymplastictransportofsugarfrommesophyllcellsto
sieve elements(loading)andsymplasticunloadinginplants.

9. Girdlingexperiment
Girdlingisanexperimentaltechniqueusedtostudytherole of
phloeminplantsphysiology.Inthisexperiment,aringofbarkis
removedfromaroundthecircumferenceofaplantstem,which
effectively cutsofftheflowofphloemsapthroughtheplants.this
processiscalledgirdling
Thegirdlingexperimentallowsresearcherstoinvestigatetheroleof
phloeminthetransportofnutrientsandotherimportantmolecules
throughouttheplants.Bystoppingtheflowofphloemsap,
researcherscanobserve theeffectsofnutrientsdeprivationon
differentpartsoftheplant.

10. Forexample,ifaplantisgirdledaboveaparticularleaf,theleafwill
eventuallyshowsignsofnutrientdeficiency,suchasyellowingorwilting,
duetothelackofsugarandothernutrientstransportbythephloem.This
demonstratesthecrucialroleofphloeminsupplyingnutrientstoplant
tissues.
Girdlingcanalsobeusedtostudytheeffectsofhormonesonplant
growthanddevelopment.Forexample,girdlingaplantstemcancausean
accumulatingofplanthormonescalledauxins,whichcanpromotethe
growthof lateralshootsandbranches.
Overall, Thegirdlingexperimentisusefultoolfor studingthefunctionof
phloemandotherimportantprocessesinplantsphysiology.

11. Reference
 https://byjus.com/question-answer/what-is-translocation-in-phloem/
 https://www.nagwa.com/en/explainers/923102368193/
 https://www.vedantu.com/question-answer/what-is-translocation-in-phloem-
class-11-biology-cbse-611b3818e41c7037fb2f30a3

12. Thank
You