Question

Define the Development of Megaspore(Megasporogenesis).

Answer 1

• Embryo sac develops from a single large cell called megaspore mother cell which has dense cytoplasm and a prominent nucleus. 
• MM cell undergoes meiosis to form four megaspores. 
• Three megaspores degenerate while one remain functional. 
• The nucleus of functional megaspore divides mitotically to form two nuclei which move to the opposite poles resulting into the formation of 2 nucleate embryosac. 
• Both two nuclei undergo two successive mitotic division forming 8 nucleate stage. 
• After that cell wall formation starts which result the formation of female gametophyte or embryo sac. 
• Three cells are grouped at micropylar end to constitute egg apparatus. 
• Three cells are grouped at chalazal end called antipodals. 
• The remaining two nuclei moves to centre of embryo sac and are called polar nuclei which fuse to form diploid secondary nucleus.