Megaspores are a type of spore found in heterosporous plants that germinate into a female gametophyte containing egg cells. Megasporogenesis is the formation of megaspores inside the ovule of seed plants. A diploid cell called the megasporocyte undergoes meiosis to form four haploid megaspores, though typically only one develops into a megagametophyte while the others disintegrate. This process of megaspore formation inside the ovule leads to the development of the embryo sac within the mature megagametophyte.

1. MEGASPOROGENESIS
MUHAMMED SADIQ

3. MEGASPORES
• Megaspores also called macrospores are a type of
spore found in heterosporous plants
• Megaspores which germinates into a female
gametophyte which produces egg cells
• These are fertilized by the male gametophyte
developing from the microspore

4. MEGASPOROGENESIS
• Megasporogenesis is the formation of megaspores
• Megaspores are formed inside the ovule of seed plants
• A diploid cell in the ovule called megasporocyte
• Megaspore mothercell undergoes meiosis and give
raise to four haploid megaspores
• In most plants only one of the megaspores develop
into megagametophyte and other 3 disintegrates

6. • In gymnosperms and flowering plants the megaspore
is produced inside the nucellus of the ovule
• Angiosperms exhibit three patterns of
megasporogenesis , monosporic, bisporic,and
tetrasporic.

7. • The megasporocyte enlarges and its cytoplasm
become very dense, the nucleus enlarges in
preparation for meiosis.
• The integuments develops from the ovule epidermis
• These envalops the megagametophyte and it become
incomplete and leave a micropyle through which
pollen tubes enters later.
• Two haploid nucei are then created.
• These divide again to produce a cell with four nuclei.
• The four haploid nuclei divide again to produce a cell
with eight nuclei this process is called free nuclear
division

9. • Following nuclear migrations and cell formation , the
mature megagametophyte ie, embryo sac id formed
• It is typically composed of an egg apparatus (
egg+2synergids) at the micropylar end of the
megagametophyte.
• Three antipodals are found at the chalazal end of the
megagametophyte