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Embriologi Tumbuhan (BI406; 2 SKS)Materi 3 dan 4
Struktur Organ Reproduksi
Angio!ermae
MegasporangiumMegasporogenesis
Megagametogenesis
An overview
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Struktur Bunga
"#ulum$ megasporangium with its
protective coats, the
integuments
%umber o& integumen$1. Unitegmic ovule
2. Bitegmic ovule
Angiosperms
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Five main types of ovuleFive main types of ovule
Classification based on the position ofmicropyle with respect to funiculus
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Relationship among the five typesRelationship among the five types
of ovulumof ovulum
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Stages in ovule developmentStages in ovule development
A. Ovule arises as a small mound of homogenous tissue on the placenta
B. Integumen arise close to the base of this tissue which forms the
nucellusC. !. "ith the differentiation of integuments, the ovule begins to curve
#. $he final shape of ovule is assumed b% the megaspore tetrad stage.
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NucellusNucellus
1. &ucellus reprecent the wall of megasporangium
2. Archesporium 'megaspore mother cell( differentiates immediatel% below
the nucellar epidermis). !epend on the thic*ening of nucellus, ovule classified into tenuinucellate,
crassinucellate, and pseudocrassinucellate.
Tenuinu'ellate o#ule
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rainu'ellate o#ule
eudo*'rainu'ellate o#ule
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Megasporogenesis andMegasporogenesis and
GametogenesisGametogenesis
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Megasporogenesis andMegasporogenesis and
GametogenesisGametogenesis
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The development of embryo sac begin withelongation of the functional megaspora,
which could be the calazal end or micropylarend of the tetrad (usually the calazal one)The elongation is largely in the micropyle-
calazal axis
The Megaspore is initially has no vacuole,the large vacuole appear later as a result ofsmall vacuoles fusionirst nuclear division in the functional
megaspore is oriented along the axis of thecell!
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+icrop%lar end
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The two daughter nuclei are pushed towardopposite poles (fig! ")
#oth nuclei divide twice forming four nuclei at eachpole (fig! #, C)
$hile the cell (megaspore) undergoing appreciableelongation, assuming a sac li%e appearance, thethree nuclei at the micropylar end organize into
egg apparatus and one nuclei is left free in thecytoplasm as the upper polar nucleus! "t the sametime, three nuclei of the calazal pole form threeantipodal cells and the fourth one function as the
lower polar nucleus (fig! &, ')The upper and the lower polar nucleus come to lie
close each other (fig! ')
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Synergid
1. Karakteristik
&ua sel yang berdampingan dengan sel telurdindingnya tida% sempurna memili%i aparatus filiform(a mass of finger-li%e proection of the wall intocytoplasm sitoplasmanya terpolarisasi (leta% va%uolalebih %earah %alaza)
2. Fungsi directing of pollen tube growth forms a seat for pollentube discharge in the embryo sac absorption andtransportation of materials from nucellus into embryosac
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Sel elur
*!Memili%i stru%tur dinding sel yang relatif samadengan synergid dan central cell (polar cell)
+!&inding di daerah mi%ropil lebih tebaldibanding%an daerah %alaza
!&alam per%embangannya, sel mengalamipolarisasi sebagai a%ibat teradinya agregasi
elemen-elemen sitoplasma pada uung %alaza!.a%uola menempati uung mi%ropil (%ebali%an dari
sinergid)
/!0itoplasmanya %aya dengan ribosom
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!ntipodal cells
*!1ara%ternya sangat bervariasi
+!#iasanya mengalami degenerasisebelum atau segera setelah fertilisasiteradi
!2ada beberapa species tumbuhanbersifat persistent (ada hubungannyadengan nutritive role bagi %antung
embrio)!3n many plant show a haustorialbehaviour
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"entral cells#$olar cells
*!The largest cell of the embryo sac+!Mother cell of the endosperm
!The nuclei (polar nuclei) are verylarge
!The nuclei fuse before or duringdouble fertilization
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! i b e d a * a n
b e r d a s a r * a n b a
n % a * n % a m e g a s p o r a % a n g
t e r l i b a t d a l a
m m
e g a g a m e t o
g e n e s i s , p e m b e n t u * a n
* a n t u n g e m
b r i o
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Monosporic
The embryo sac is derived from onlyone magaspore
1.Polygonum type4 the embryo sac isformed by chalazal megaspore with
three time mitosis
2.Oenothera type4 the embryo sac isformed bay micropylar megaspore
with two time mitosis
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&isporic- The embryo sac is derived from two magaspore- 2embelahan meiosis pertama berlangsung
sempurna, tetapi hanya salah satu sel ana%yang mela%u%an meiosis %edua! 0atu sellainnya degenerasi!
- 1edua megaspore mela%u%an pembelahanmitosis dua %ali membentu% %antung embriodengan 5 inti
1. Alium type4 the embryo sac is derived fromchalazal dyad cell
2.Endymion type4 the embryo sac is derived frommicropylar dyad cell
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etrasporic
- The embryo sac is derived from four magaspore
- Teradi %arena pembelahan meiosis 3 dan 33 tida%dii%uti dengan pembentu%an dinding sel, shg intisel hasil meiosis berada dalam satu sel(coenomegaspore)
-
1eempat inti dalam coenomegaspore terlibatdalam pembentu%a %antung embrio
- 6uclear behaviour is 7uite variable (see slide *5),depend on the arrangement of the four nuclei(*8*8*8* in Paperomia, Penaea, and Plumbago
type *8 in Drusa, Fritilaria, Plumbagella type+8+ in Adoxa type)