Question
With a labeled diagram write a short note on formation of embryo sac.###Explain internal structure of embryo sac###With a neat diagram, explain the 7-celled, 8 nucleate nature of female gametophyte.
✓
Answer
→ The female gametophyte is formed by the mitotic division of the functional megaspore.
→ The megaspore divides mitotically thrice to form 8 nucleate embryo sacs. The process of formation of 7-celled, 8 nucleate nature of female gametophyte is mentioned below :
→ Two nuclei are formed after the cell undergoes first mitotic division.
→ These two nuclei move towards the micropylar end and the chalazal end, respectively.
→ They divide and redivide to form 8 nucleate stage.
→ Consequently, there are four nuclei each on either ends.
→ At the micropylar end, three out of the four nuclei differentiate into an egg cell and synergids.
→ At the chalazal end, three out of the four nuclei differentiate as antipodal cells.
→ The remaining cells, each from either ends move towards the centre and are known as polar nuclei.
→ Therefore on maturation, the female gametophyte looks like a 7-celled structure.
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