Syngamy, Biology

Syngamy

The pollen tube grows to a very limited extent in the synergid. It releases the contents either through a terminal or a subterminal pore. The contents include the two male gametes along with the accompanying cytoplasm, some reserve nutrients and perhaps vegetative nucleus. One of the sperms enters the egg and the other to the central cell. The distance that the male gamete has to travel to come in contact with the egg or secondary nucleus is insignificant. The male gamete comes in contact with the plasma membrane of the egg that forms a bridge through which the male gamete enters.

Nuclear fusion is initiated by the joining of the outer membrane of the two nuclei. The inner membrane also fuses at localized areas forming a small bridge between the two nuclei. Enlargement of bridge causes eventual fusion of the male and egg nuclei (syngamy). Depending upon the stage of the male gamete at the time of nuclear fusion, three types have been recognized. (a) in pre-mitotic type-the male nucleus fuses with the egg before reaching the mitotic inter phase, (b) in post-mitotic type the male nucleus undergoes inter phase while in contact with the egg and the fusion is postponed until the initiation of the first mitosis in both, and (c) in intermediate cases, the fusion occurs when male nucleus is still at interphase. Generally, the male cytoplasm does not take part in fertilization. However, there are plants in which biparental inheritance of plastids has been demonstrated.

Posted Date: 1/23/2013 4:46:37 AM | Location : United States







Related Discussions:- Syngamy, Assignment Help, Ask Question on Syngamy, Get Answer, Expert's Help, Syngamy Discussions

Write discussion on Syngamy
Your posts are moderated
Related Questions
What is Colloids and Suspensions ? Colloids and Suspensions :  Colloids and suspensions are mixtures in which larger particles replace solutes. Colloids, or colloidal suspe

Explain about Osteogenesis Osteogenesis, large amounts of woven bone can be formed very rapidly. This bone is believed to be much more compliant than organized lamellar bone. I

Define Biosynthesis and Secretion of Thyroid Hormones? Histologically, the functional cells of the thyroid gland are arranged in follicles, which surround a central lumen conta

What are the main cytoplasmic structures present in animal cells? Ans) The major cytoplasmic structures of the cell are the centrioles, the cytoskeleton, lysosomes, mitochondria

What is Probing depth Probing depths can be influenced by the tissue type- shallow depths are associated with a keratinized collar, whereas deeper depths are associated with mo

Secondary Induction The two primary inductive events that we have described so far are significant in the patterning of early embryo. But there are another such signaling eve

Q. What is the difference between obligate anaerobic beings and facultative anaerobic beings? Obligate anaerobic beings are those that cannot survive when oxygen is present. So

Q. What do active transport and facilitated diffusion have in common? What are the dissimilarity between them? Facilitated diffusion can be perplexed with active transport beca

Describe the terms diffusion, osmosis and filtration. Explain why each process is important for the human body.

ADP-ATP system  of energy  exchange : In 1929 Lohmann, Fiske and  subbarow  published  their  discovery  that the energy  exchanges  compounds in all biological  systems  are t