Recurrent type, Biology

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







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
Related Questions
Q. Optional use values of biodiversity? Optional values are associated with potential use in the future. Accordingly one opts to conserve biodiversity based on the hope that it

What is Lactate Lactate is transported to  the liver in  the Cori cycle (lactic  acid cycle)  and is converted to pyruvate. Hepatic gluconeogenesis then converts  lactate  ba

What is a terrestrial organism? 'Terra' is the Latin word for earth. Thus, an animal that lives on the surface of the earth is known as terrestrial. This is the similar root wo

What is the life cycle type of bryophytes? As in all plants the life cycle of bryophytes is diplobiontic (alternation of generations). In bryophytes the lasting form is the hap

Solutes and ions tie up water in solution. Solutes lower aw and this reduction in aw depends on the total concentration of dissolved molecules and ions. Since these bind to water m

Chemiosmosis is the process by which the ATP is produced in inner membrane of a mitochondrion. It is the electron transport system transfers protons from the inner compartment to

How do calcium ions participate in muscle contraction? Why do both muscle contraction and muscle relaxation spend energy? In the muscle cells calcium ions are kept within the s

PROJECTS THAT HAVE TO BE DONE IN SCHOOL ABOT PICICULTURE

Tongue grafting Top of the stock is cut diagonally and in an upward direction. Scion is cut diagonally in downward direction. A second cut is given from above downwards,

Speculate on the necessity of interdependence of volvox organisms in the colonial existence