Sexual Reproduction In Flowering Plants
Formation of Megaspores (Megasporogenesis)
A single megaspore mother cell in the ovule undergoes meiotic division in the micropylar region of the nucellus. Meiotic division results in the formation of four megaspores. ‘The process of formation of megaspores from the megaspore mother cell is called megasporogenesis.’ Go through the illustration to get a clarity on the concept.
Embryo Sac Formation
Megaspore mother cell undergoes meiotic division to produce four daughter cells. One megaspore is functional while the rest three degenerate. The functional megaspore develops into embryo sac or female gametophyte. Formation of embryo sac from one megaspore is termed as monosporic. Nucleus of active megaspore divides mitotically thrice to form 8 nuclei. The embryo sac is a 7-celled, 8-nucleate structure. The given illustration guides you through all the steps of embryo sac formation.
Structure of the Megasporangium (Ovule)The ovule remains attached to the placenta through the funicle. Body of funicle and ovule fuses at the junction called hilum. Ovule has outer protective coverings called integuments the protective covering can be one layered or two. Integuments form the covering throughout the nucellus except at the tip, where a small opening called micropyle is present. This end of the ovule is called micropylar end and the end opposite to the micropylar region is chalazal end. Chalaza is the basal part of the ovule. Explore the given video for the understanding of the structure of an ovule.
Difference between Microsporogenesis and Megasporogenes is the formation of microspores from a pollen mother cell whereas megasporogenesis is the formation megaspores from megaspore mother cell. One of the processes takes place in pollen sac while other in the ovule. A table stating differences between the two is given to understand both the processes clearly.
Embryogenesis in Dicot Plants Double fertilization leads to the formation of zygote and primary endosperm nucleus. This primary endosperm nucleus develops into endosperm followed by development of zygote into embryo.