How do pollen cells form

During the second phase, megagametogenesis , the surviving haploid megaspore undergoes mitosis to produce an eight-nucleate, seven-cell female gametophyte, also known as the megagametophyte or embryo sac.

Two of the nuclei—the polar nuclei —move to the equator and fuse, forming a single, diploid central cell. This central cell later fuses with a sperm to form the triploid endosperm. Three nuclei position themselves on the end of the embryo sac opposite the micropyle and develop into the antipodal cells, which later degenerate.

The nucleus closest to the micropyle becomes the female gamete, or egg cell, and the two adjacent nuclei develop into synergid cells Figure 3. The synergids help guide the pollen tube for successful fertilization, after which they disintegrate. Once fertilization is complete, the resulting diploid zygote develops into the embryo, and the fertilized ovule forms the other tissues of the seed.

A double-layered integument protects the megasporangium and, later, the embryo sac. The integument will develop into the seed coat after fertilization and protect the entire seed.

The ovule wall will become part of the fruit. The integuments, while protecting the megasporangium, do not enclose it completely, but leave an opening called the micropyle. The micropyle allows the pollen tube to enter the female gametophyte for fertilization. An embryo sac is missing the synergids. What specific impact would you expect this to have on fertilization?

Improve this page Learn More. Skip to main content. Module 9: Plant Reproduction. Search for:. Sexual Reproduction in Angiosperms Learning Outcomes Identify the structures involved in reproduction of angiosperms. Practice Question An embryo sac is missing the synergids. Resources and Planting Guides.

Cultivating a Natural Habitat for Nesting. How to Make Nesting Structures. Certification Programs. What is Pollination? Cross Pollination vs. Self Pollination. What is Fertilization. How Does the Ovule Develop? How Does the Pollen Grain Develop? Apidae — Bumblebees. Apidae — Carpenter bees, Squash bees, Blueberry bees, Cuckoo bees. Megachilidae — Leafcutter and Mason bees.

Halictidae — Sweat bees. The generative cell subsequently detaches from the pollen grain wall and is engulfed by the vegetative cell forming a unique 'cell within a cell' structure. The engulfed generative cell divides once more by mitosis pollen mitosis II to form the two sperm cells completely enclosed within the vegetative cell cytoplasm either before pollen is shed tricellular pollen or within the pollen tube bicellular pollen.

Personal tools Web Editor Log in. Search Site only in current section. Advanced Search…. Search Site. Pathways of pollen development Pollen is produced within the anthers microsporangia or pollen sacs of the flower. Microsporogenesis and microgametogenesis Two distinct and successive developmental phases, microsporogenesis and microgametogenesis, lead to the production of the mature microgametophytes.