2
Question
With a neat, labelled diagram, describe the parts of a mature
angiosperm embryo sac. Mention the role of synergids.
angiosperm embryo sac. Mention the role of synergids.
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Solution
Parts of embryo sac of an angiosperm
A typical mature embryo sac of an angiosperm is composed of seven cells and eight nuclei. They are as follows:-
● Egg apparatus with one egg and two synergid cells
● Three antipodal cells
● Two central polar nuclei remain free until fertilisation
by male gamete.
Egg apparatus
The egg apparatus is present at the micropylar end and is composed of an egg and two synergids.
Antipodal cell
Three antipodals are present at the chalazal end.
Central polar nuclei
Two polar nuclei are present in the centre and form a diploid secondary nucleus.
Role of synergids
Synergids consist of a filiform apparatus ( thickening of the cell wall facing the micropylar tip) that directs the movement of the pollen tube inside the embryo-sac.
A typical mature embryo sac of an angiosperm is composed of seven cells and eight nuclei. They are as follows:-
● Egg apparatus with one egg and two synergid cells
● Three antipodal cells
● Two central polar nuclei remain free until fertilisation
by male gamete.
Egg apparatus
The egg apparatus is present at the micropylar end and is composed of an egg and two synergids.
Antipodal cell
Three antipodals are present at the chalazal end.
Central polar nuclei
Two polar nuclei are present in the centre and form a diploid secondary nucleus.
Role of synergids
Synergids consist of a filiform apparatus ( thickening of the cell wall facing the micropylar tip) that directs the movement of the pollen tube inside the embryo-sac.
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