female gametophyte
TRANSCRIPT
Wel-Come
Female Gametophyt
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Female Gametophyt
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FEMALE GAMETOPHYTE
Female Gametophyte
Central cell with 2 polar nuclei
Female Gametophyte
Egg apparatus• one egg cell• two synergids
Female Gametophyte
Chalazal End * 3 antipodal cells
Development Of Embryo Sac
Begins with elongation of functional megaspore.
Elongation is largely in micropylar chalazal axis
•Non-Vacuolated megaspore
cytoplasm later developed with small sized vacuoles.• In later period they may fuse
together to form large sized vacuoles.
Stages In Megagametogen
esis
Megaspore after first-meiotic mitosis•A large central vacuole now appears between the two daughter nuclei.
•On further expansion of vacuole the nuclei are pushed towards opposite poles of the cell.
Four Nucleate Stage
Both the nuclei
divide twice,
forming 4 nuclei at
each pole
Eight Nucleate
Stage
Again divides to form 8 nucleate stage
3 + 2 + 3 Distribution
•All the 8 nuclei are in a common cytoplas - m•Soon after this division cell elongates and gains the sac like appearance
Mature Embryo Sac
• 3 – celled egg apparatus•3 – antipodal cell•Large central cell with Secondary nucleus
Mature Embryo Sac
•
Types Of Embryo Sac
• Monosporic Embryo Sac• Bisporic Embryo Sac• Tetrasporic Embryo Sac
Depending upon the number of megaspore nuclei involved in the formation of Eembryo Sac
Monosporic Embryo Sac
FeaturesIt is derived from only one of the four
megaspores.Al the nuclei are genetically
identical, because they are derived through mitoses of a single nucleus.
Types Of Monosporic Embryo Sac
Polygonum It is formed by the chalazal megaspore
of the tetrad & is 8 nucleate. It Consists,* 3 celled egg apparatus* 3 antipodal cells* binucleate central cell.
Types Of Monosporic Embryo Sac
Oenothera type It is formed by the micropylar
megaspore of the tetrad & is 4 nucleate. It Consists,
* 3 celled egg apparatus* uninucleate central cell.
Types Of Bisporic Embryo Sac
Features Formation of dyad cell. Among 2 one undergoes 2nd meiotic division and other one degenerates. Bisporic is derived from 2 meiotic products and their nuclei belongs to 2 different genetic constitutions.
Types Of Bisporic Embryo Sac
Allium Type The embryo sac is derrived from the chalazal dyad cell.
EndymionThe embryo sac is derrived from the micropylar
dyad cell.
Types Of Tetrasporic Embryo SacNo wall formation takes
place. Hence at the end of meiosis all the 4 haploid nuclei in a common cytoplas - m forming coenomegaspore.
All the 4 nuclei of the coenomega -spore take part in the formatio n of embryo sac. Due to the meiosis all nucleus are genetically different.
Tetrasporic – Adoxa Type
Embryo sac is 8 nucleate & formed after the post-meiotic mitosis.
Tetrasporic – Plumbago type
Only one post meiotic mitosis occurs. The mature embryo sac consists an - Egg cell
- 4 nucleate central cell
Other 3 nuclei are cut off as peripheral cell.
Tetrasporic – Penea Type
Due to 2 post-meiotic motises in the coenomegaspore 16 nuclei are formed. It consists 4 groups of 3 cell each,
- one at the micropylar end- one at the chalazal end- two arranged laterally
Remaining 4 behaves as polar Egg apparatus – micropylar triad
Tetrasporic – Peperomia Type
The embryo sac is 16 nucleate . The organization of mature sac is
- Ony one egg and synergids- six peripheral cells- central cell with 8 polar nuclei
Tetrasporic - Drusa
It is also 16 nucleate. It consists
- 3 celled egg apparatus- 2 polar nuclei- 11 antipodal cells
Tetrasporic – Fritillaria
After the nuclear fusion both nuclei of the coenomegaspore( one 1N and one 2N) divide twice forming 4 nuclei at each pole. The mature embryo sac comprises an
- egg apparatus of 3 1N cells.- 3 triploid antipodal cells- Central cell with 2 polar nuclei one
1N and one 2N
Tetrasporic – Plumbagella Type
After a nuclear division of each nucleus 4 nuclei are formed. Two at micropylar and 2 at the chalazal end. One of the haploid nuclei at the micropylar forms egg and other one acts as upper polar nucleus
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