microsporangium of the science-180808174128.pdf

Science project class 11

1. Microsporangium
Presented by : SalviPinky P.
M.sc sem-2
Botany -404
Department of Life Sciences ,
H. N. G. U., Patan

2. Introduction
Developmentof microsporangium
Antherwall
Sporogenoustissue
Microsporogenesis
Content

3. Introduction
•Microsporophyllorthestamenisthemalereproductive
partoftheflower,whichconsistsfilament,antherand
connective.
•Antheristhefertilepartofmicrosporophyllsometimesit
issterilecalledstaminode.
•Thefilamentistheslenderstalkofthestamenandthe
antheristheexpendedheadbornebythefilamentatits
tip.

4. Structure of Stamen

5. Development of microsporangium
•Ineachlobeafewcellsinthehypodermalregionbecome
differentiatedbytheirlargesize,radialgrowth,densecytoplasm
andconspicuousnuclei.
•Thereismuchvariationinthenumberofcellsofarchesporium.
•Generally,thearchesporiumconsistsofatwotothreecell,wide
platerunningalongtheentirelengthofthelobe.
•Theextentofarchesporiumvariesbothlengthwiseandbreadth
wise.

7. The wall of microsporangium
•Theepidermisalongwiththe3–5layersderivedfromthe
primaryparietallayerformthewallofthesporangium.
•Thecellsoftheepidermisdevideanticlinallyonly.
•Thecellsthusformedbecomegreatlystretchedandflattened.
•Sometimesitscellsmaybecomegreatlylignifiedorcutinized.
•Amatureantherwallconsistsof4layers:
A)epidermis
B)endothecium
C)middlelayer
D)tapetum

9. •Typesoftapetum:-
1)AmoeboidalTapetum:-
a)Sagittariatype
b)Butomustype
c)Sparaganiumtype
d)Triglochintype
2)SecretoryorGlandularTapetum

10. Sporogenous Tissue
•Theprimarysporogenouslayercellsgiverisetothemicrospore
mothercellsorthepollenmothercells.
•Thesporogenouscellsinnormalwaydivideseveraltimes
mitoticallybeforefunctioningaspollenmothercells.
•Incertaincasestheprimarysporogenouscellsmayeithershow
onlyfewdivisionsornodivisionsatcell,thusgivingrisetoavery
smallgroupofsporogenouscellsortheprimarysporogenouscells
themselvesfunctiondirectlyasthemicrosporemothercells.

11. Microsporogenesis
•Themicrosporemothercellswhichareatfirstpolygonaland
closelypackedgraduallybecomeroundedandlooselyarrangedin
therapidlyenlargingmicrosporangium.
•Eachfunctionalsporemothercellproducesfourmicrosporeor
pollengrains.
•Typesofmicrosporogenesis:-
A)Meiosis
B)Cytokinesistype:-
1)Successivetype
2)Simultaneoustype:-
a)Tetrahedral
b)Isobilateraltetrad
C)Decussatetetrad
d)T–shaped
e)Lineartetrad
3)Thepollengrains

13. Cytokinesis type : -
•Thedivisionofthemicrosporemothercellsmaybeforthe
successiveandsimultaneoustype.
•Inthesuccessivetype,acellplateisdevelopedimmediatelyafter
thefirstmeioticdivisionandanotherineachofthetwodaughter
cellsafterthesecondmeioticdivision.
Successivetype:-
•Inthistypeacellwallislaiddownbetweenthetwodaughter
nucleiimmediatelyaftertheirformationduringthefirstmeiotic
division.
•Thesecondmeioticdivisiontakesplaceformingtwodaughter
cells.
•Andthenagainawallisformedinifthetwodaughtercells.

14. Simultaneous type : -

15. •Thistypeiscommonlyformedindicotyledonsplants.
•Inthiscasethenucleusofthemicrosporemothercelldivides
twiceformingfourhaploidnucleilayinginthecommonmassof
cytoplasmofthemothercell.
•The4nucleithusformedarebeingarrangedintetrahedral
mannerandaftercleavageofcytoplasmthe4distinctsegments
areformed.
Thepollengrains:-
•Thepollengrainsormicrosporesarethemalereproductive
bodiesofaflower,andarecontainedinthepollensacor
microsporangium.
•Theyareveryminuteinsize,andarelikeparticlesofdust.
•Eachpollengrainsconsistsofasinglemicroscopiccell,possessing
twocoats:-1)theexine
2)theintine

16. Structure of the pollen grains :

17. References
•A Taxt book Of botany : Angiosperms :
by : -B. P. Pandey
https://www.kullabs.com
https://en.m.wikipedia.org
https://www.pnas.org

18. THANK YOU