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प्रश्न
Embryo sacs of some apomictic species appear normal but contain diploid cells. Suggest a suitable explanation for the condition.
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उत्तर
It is true that many apomicts posses normal-looking embryo sacs. The only possibility of the embryo sac possessing diploid cells is due to failure of meiotic division at the megaspore mother cell stage. Since, the megaspore mother cell has a dipoid nucleus, if it undergoes mitosis instead of meiosis, all the resulting nuclei and cells will be diploid in nature.
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संबंधित प्रश्न
The method of embryo sac forming from a single megaspore is called ______.
In a flower, if the megaspore mother cell forms megaspores without undergoing meiosis and if one of the megaspores develops into an embryo sac, its nuclei would be ______.
Name the component cells of the ‘egg apparatus’ in an embryo sac.
Draw the diagram of a mature embryo sac and show its 8-nucleate, 7-celled nature. Show the following parts: antipodals, synergids, egg, central cell, polar nuclei.
With a neat, labelled diagram, describe the parts of a mature angiosperm embryo sac. Mention the role of synergids.
Explain the monosporic development of the embryo sac in the ovule of an angiosperm.
The female gametophyte of angiosperms is called the embryo sac. How many cells and nuclei does a mature embryo sac contain?
During the development of the female gametophyte, the functional megaspore undergoes mitotic divisions without immediate cell wall formation. What are these divisions called?
In the first mitotic division of the functional megaspore, the two daughter nuclei move to opposite poles of the enlarging megaspore. What stage is this called?
Following the 2-nucleate stage, both nuclei divide simultaneously during the second mitotic division. What is the resulting stage called, and how many nuclei are at each pole?
The central cell of the mature embryo sac contains two polar nuclei. What is the ploidy level of the central cell after the two polar nuclei fuse?
The mature embryo sac is described as monosporic and of the Polygonum type. What does the term monosporic indicate about the origin of the embryo sac?
What is the total number of haploid nuclei present in the 8-nucleate stage of the developing female gametophyte before cell walls are formed?
During the development of the embryo sac, which stage immediately precedes the formation of the polar nuclei by migration?
How many mitotic divisions are required to convert the haploid functional megaspore into the 8-nucleate stage?
In the mature embryo sac, which structure contains the filiform apparatus that aids in guiding the pollen tube?
