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

Define citric acid cycle, The citric acid cycle also called as the TCA cycl... The citric acid cycle also called as the TCA cycle (tricarboxylic acid cycle) and the Krebs cycle or the Szent-Györgyi-Krebs cycle is a series of chemical reactions used by all aer

What do numeric pyramids represent?, What do numeric pyramids represent? ... What do numeric pyramids represent? The Numeric pyramids represent the number of individuals in each trophic level of a food chain.

Circulatory system - developmental changes, Circulatory System - Developmen... Circulatory System - Developmental Changes We have learnt that throughout foetal life, gas exchange takes place, only through the placenta and not through lungs. Therefore, t

What is osseointegration in macroscopic biomechanical, Q. What is Osseointe... Q. What is Osseointegration in macroscopic biomechanical? A fixture is osseointegrated if there is no progressive relative motion between the fixture and surrounding living bon

The neural impulse is transmitted along the axon, What is the mechanism by ... What is the mechanism by which the neural impulse is transmitted along the axon? The neural impulse is transmitted with the neuronal membrane through depolarization of consecu

Dicots, Dicots are one of the two main types of flowering plants; characte... Dicots are one of the two main types of flowering plants; characterized by having two cotyledons, floral organs arranged in the cycles of four or five, and leaves with the reticul

Zoology, Write briefly on neural mechanism of learning? Write briefly on neural mechanism of learning?

Qualitative changes, Qualitative Changes The qualitative changes in th... Qualitative Changes The qualitative changes in the structure of proteins in response to stress can lead to the following: Resistance against denaturation of prote

Food hygiene, as newly appointed food safety manager within a medium seized... as newly appointed food safety manager within a medium seized

Infectious and chronic diseases, Infectious and Chronic Diseases The m... Infectious and Chronic Diseases The most prevalent diseases of poverty, many of which are also infectious by nature, are malaria, tuberculosis, respiratory infections, water b