Q. 145.0( 1 Vote )
The embryo sac in
A matured embryo sac contains an egg apparatus, antipodal cells and central cell.
• located in the micropylar end
• Constitute three cells which are grouped together.
• They are two synergids and one egg cell.
• Synergids guide the entry of pollen tube. It has a special cellular thickening at the micropylar tip called filiform apparatus.
• An egg cell has the female gamete.
• Three cells in the chalazal end are the antipodal cells.
• It is a large cell
• Central cell constitutes two polar nuclei.
Hence a total of 7 celled (3 antipodal cells, one central cell, 2 synergids, 1 egg cell) and 8 nucleate (3 antipodal nuclei, 2 polar nuclei, 2 synergids nuclei, 1 female gamete nuclei) makes the nature of female gametophyte.
In angiosperms, the seed is the final product of sexual reproduction. It is often described as a fertilized ovule.
Steps involved in the maturation of an ovule into a seed:
• Integuments of the ovule harden as tough to produce protective seed coats.
• Micropyle remains as a small pore in the seed coat. It facilitates the entry of oxygen and water into seed during germination.
• As seed matures, the water content is reduced and become relatively dry.
• The metabolic activities of the embryo slow down.
• Embry enters into a state of inactivity called dormancy.
• Germination on availability of favourable conditions (adequate moisture, oxygen and suitable temperature).
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