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Zorluk: OrtaReproductive Systems and Processes in Organisms

During double fertilization in flowering plants, one haploid generative nucleus fuses with the egg cell to yield a diploid zygote. What is the ultimate fate and ploidy of the second generative nucleus?

  1. It fuses with two polar nuclei to form a triploid endosperm nucleusCevap
  2. B
    It fertilizes a synergid cell to produce a diploid protective seed coat
  3. C
    It combines with antipodal cells to form a haploid nutritive layer
  4. D
    It adheres to feathery stigmatic surfaces to stimulate pollen tube extension

Cevap

The second generative nucleus fuses with two polar nuclei in the embryo sac central cell to form a triploid (3n3n) primary endosperm nucleus.
In flowering plants, double fertilization involves two distinct fusion events inside the embryo sac. While one male gamete (nn) fertilizes the egg (nn) to form the diploid zygote (2n2n), the second male gamete (nn) fuses with the two polar nuclei (n+nn + n) in the central cell. This process is called triple fusion, forming a triploid (3n3n) primary endosperm nucleus that later develops into endosperm tissue.

Adım Adım Çözüm

1
Identify the gamete composition inside the angiosperm pollen tube
The pollen tube contains two haploid (nn) male generative nuclei (sperm cells).
Angiosperms undergo double fertilization requiring two separate fusion events within the female gametophyte.
2
Trace the first fertilization event
One male gamete (nn) fuses with the egg cell (nn) to form the diploid (2n2n) zygote.
This represents syngamy, which gives rise to the plant embryo.
3
Trace the second fertilization event (triple fusion)
The second male gamete (nn) fuses with two central polar nuclei (n+nn + n) to yield a triploid (3n3n) primary endosperm nucleus.
This fusion of three haploid nuclei (triple fusion) develops into the endosperm, which stores food reserves for the germinating seed.

Anahtar Kavram

Double Fertilization and Triple Fusion in Angiosperms
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Konular

Reproductive Systems and Processes in Organisms

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