Recurrent Type

In this type, euspory (seen in normal cases) is replaced by aneuspory (Diplospory) because of irregular meiosis. When the spore mother ceIl functions directly as the embryo sac initial it is termed gonial apospory and when one or more of the somatic cells of the nucellus or chalaza act as embryo sac initial it is called somatic apospory.

Aneuspory (Diplospory)

Includes cases in which during spore formation the meiotic process is irregular. Depending upon the extent of irregularity in meiosis in various plants, aneuspory is further categorized into various types.

• Datura type - the two unreduced nuclei undergo two mitotic divisions to produce an 8-nucleate embryo sac.
• Taraxacum type - first meiotic division ends in a restitution nucleus. Meiosis II produces unreduced cells. Ultimately an 8-nucleate embryo sac is formed. The egg directly forms the embryo.
• Ixeris type - it is like Taraxacum, but a single binucleate gynophore is formed. Two divisions lead to the formation of an 8-nucleate embryo sac.
• Allium type - a premeiotic-endomitotic doubling makes meiotic prophase to start with double chromosome number. The result is an unreduced embryo sac.

Posted Date: 1/23/2013 5:55:47 AM | Location : United States

Ask an Expert

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

Write discussion on Recurrent type
Your posts are moderated

Write your message here..

Related Questions

Adenosine triphosphate (atp), Adenosine triphosphate (ATP) is a general fo... Adenosine triphosphate (ATP) is a general form in which the energy is stored in living systems; comprises of a nucleotide (with ribose sugar) with three phosphate groups. Energy c

Cavity development, A complete gut is sometimes called tube within a tube. ... A complete gut is sometimes called tube within a tube. Why?

What are the main divisions and representing species, What are the main div... What are the main divisions and representing species of the gymnosperms? This group of plants can be divided into conifers (pine, sequoia, cypress), that have flowers known as

What is radiographic template, What is Radiographic Template Radiograp... What is Radiographic Template Radiographic Template : You should always use it while taking a panoramic radiograph of the patient. It is done to counter the effect of magnific

Nucleic acids, Nucleic Acids Friedrich Miescher  (1868) discovered the ... Nucleic Acids Friedrich Miescher  (1868) discovered the presence  of these compound  in protoplasm ,but Altman (1889) introduced the term Nucleic acid. These  acids are the lar

Chemical changes during cleavage, CHEMICAL CHANGES DURING CLEAVAGE - 1.... CHEMICAL CHANGES DURING CLEAVAGE - 1.       Synthesis of DNA occurs. 2.       Synthesis of RNA (rRNA is absent, mRNA & tRNA are synthesized very little amount). 3.

Feline panleukopenia, Feline panleukopenia It is arguably the most importa... Feline panleukopenia It is arguably the most important of all feline viral diseases and all members of the family Felidae are susceptible. This disease is commonly found in kitten

Define the food and nutrition security, Define the Food and Nutrition Secur... Define the Food and Nutrition Security? In the previous section, we learnt about the trends in production of food grains in the country and their relationship to population gro

Define the microbiological study of water, Define the Microbiological Study... Define the Microbiological Study of Water? Water is a common carrier of infectious diseases. Even clean and clear water which looks pure may be contaminated with pathogenic mic

Oxygen affecting the growth of microorganism, oxygen affecting the growth o... oxygen affecting the growth of microorganism? The presence of oxygen in the atmosphere is required for the survival of human beings. Contrary to this, you would realize that th