Agamospermous Embryo Sac Development:
Agamospermous embryo sac development refers to the formation of an embryo sac without fertilization. This process can occur through various mechanisms such as pollen, egg, ovum, or megaspore mother cell. Let's explore how each of these processes leads to the development of an embryo sac.

1) Pollen:
In the case of agamospermous embryo sac development from pollen, the pollen grains undergo a process known as sporophytic apomixis. Here, the pollen grains germinate and directly form an embryo sac without the need for fertilization. This process results in the development of an embryo sac containing an embryo without genetic recombination.

2) Egg:
When agamospermous embryo sac development occurs from an egg, it involves the formation of an embryo sac from an unfertilized egg cell. This process can be triggered by various factors such as stress or hormonal cues, leading to the development of an embryo within the embryo sac without the involvement of male gametes.

3) Ovum:
In some cases, agamospermous embryo sac development can take place directly from an ovum. The ovum undergoes divisions and differentiation to form an embryo sac without fertilization. This process results in the formation of an embryo sac with an embryo that is genetically identical to the parent plant.

4) Megaspore Mother Cell:
Agamospermous embryo sac development can also occur from a megaspore mother cell. The megaspore mother cell undergoes meiosis to produce a megaspore, which then develops into an embryo sac without fertilization. This process results in the formation of an embryo sac containing an embryo that is genetically identical to the parent plant.
In conclusion, agamospermous embryo sac development can occur through various mechanisms such as pollen, egg, ovum, or megaspore mother cell. Each of these processes leads to the formation of an embryo sac without the need for fertilization, resulting in the development of an embryo with genetic similarities to the parent plant.