How many nuclei are present in Fritillaria type of embryo sac?
12) producing a 7-nucleate embryo sac with four nuclei at the micropylar end and three at the chalazal.
Which is Bisporic type embryo sac?
Bisporic embryo sacs contain nuclei derived from two members of a megaspore tetrad whereas tetrasporic embryo sacs contain nuclei derived from all four members of a tetrad. Megaspores from the same tetrad are less genetically similar than are megaspores from different tetrads.
Which one of the following is the example of tetrasporic type of embryo sac?
It is also called the Allium type of embryo sac. Therefore, the correct answer is option B. Note: In the tetrasporic type of embryo sac, a single megaspore is formed after meiosis which contains 4 haploid nuclei. It is also called the Peperomia type of embryo sac.
Why is this type of embryo sac development called as Monosporic?
The megaspore mother cell or MMC contains a dense cytoplasm and a large nucleus. The megaspore mother cell divides by meiotic division to give rise to 4 haploid megaspores. Generally, only one megaspore is functional and develops into the female gametophyte or the embryo sac. This is known as monosporic development.
What is Fritillaria type?
Fritillaria (fritillaries) is a genus of spring flowering herbaceous bulbous perennial plants in the lily family (Liliaceae). The type species, Fritillaria meleagris, was first described in Europe in 1571, while other species from the Middle East and Asia were also introduced to Europe at that time.
What are the 8 nuclei present in embryo sac?
Both the nuclei of the functional dyad take part in the formation of embryo sac. Each nucleus undergoes two mitotic divisions and the mature embryo sac is 8 nucleated. The eight nuclei are organised into antipodals, egg apparatus and polar nuclei as in Polygonum type of embryo sac.
What is triple fusion?
Definition of triple fusion : the fusion involving two polar nuclei and a sperm nucleus that occurs in double fertilization in a seed plant and results in the formation of the endosperm.
What is polygonum type of embryo sac?
The normal or polygonum type of embryo sac is a monosporic eight nucleate. The embryo sac develops from the chalazal megaspore. Its nucleus divides thrice to form eight nuclei. This type is known as normal or polygonum type (first time described in polygonum divaricatum by Starsburger) of embryo sac.
What is meant by Tetrasporic embryo sac?
All the four nuclei of coeno-megaspore participate in the formation of the embryo sac. This type of embryo sac is called as tetrasporic like in Peperomia. The four haploid nuclei of coeno-megaspore undergo two successive mitotic divisions forming 16 nuclei.
What does Monosporic development mean?
The formation of the female gametophyte from a single functional megaspore is called as monosporic development. The nucleus of functional megaspore divides mitotically to form two nuclei which move to opposite poles.
What are the type of embryo sac?
Based on the number of megaspores, embryo sacs can be divided into three types: monosporic, bisporic, and tetrasporic (Web Figure 21.3. A). In the monosporic, or Polygonum-type embryo sac, meiosis of the diploid megaspore mother cell in the nucellus produces four haploid megaspores.
What kind of embryo sac has four megaspores?
Monosporic, Normal or Polygonum Type It is commonly found in plant. It is commonly called normal type. However, it was first clearly described in Polygonum. Therefore, it is also called as Polygonum type. This embryo sac has four well-defined megaspores.
How is an 8 nucleate embryo sac formed?
The 8-nucleate embryo sac is formed by the nuclear divisions of the upper cell of the dyad. This type of embryo sac development was first observed in Endymion hispanicus (Battaglia, 1958). 3. Tetrasporic Type:- In this type of embryo sac there are several variations.
What kind of type of embryo sac is bisporic?
Bisporic Type:- Bisporic type of embryo sac development is also known as allium type. In this type two of the four megaspores take part in the development of female gametophyte.
What makes up the embryo sac in angiosperms?
The monosporic 8-nucleate embryo sac, formed by three divisions of the functioning megaspore, occurs in at least 70 per cent of the angiosperms now known. The enlargement of the megaspore is always accompanied by increased vacuolation, one large vacuole usually appearing on either side of the nucleus in the direction of the long axis of the cell.