याद रखने योग्य अवधारणाएँ और फॉर्मूला
Development of Embryo Sac in Angiosperms:
Megasporogenesis: Begins with the formation of megaspores from the megasporocyte within the ovule.
Functional Megaspore: One out of four megaspores becomes the functional megaspore, while the others degenerate.
Female Gametophyte: The functional megaspore undergoes mitotic divisions, forming the female gametophyte or embryo sac.
Components of Embryo Sac: The embryo sac typically consists of seven cells and eight nuclei:
- Three Antipodal Cells
- Two Synergid Cells
- One Egg Cell (Oosphere)
- Two Polar Nuclei
Pollen Tube Guidance: Synergid cells guide the pollen tube toward the egg cell for fertilization.
Fertilization: The pollen tube delivers sperm cells. One sperm cell fuses with the egg cell to form a zygote, while the other fuses with polar nuclei to initiate endosperm formation.
Embryo Development: The zygote within the embryo sac develops into the future plant embryo. Synergids are pair of haploid cells present at the micropylar end of embryo sac. Zygote which is a diploid structure undergoes divisions to form an embryo. Antipodal and polar nuclei are also haploid in nature. Primary endosperm nucleus is triploid in nature. In a fertilized embryo sac the haploid, diploid and triploid structures are synergid, zygote and primary endosperm respectively.
Seed Formation: The mature embryo sac, with the embryo and endosperm, leads to seed formation within the ovule.