Question

Functional megaspore in an angiosperm develops into-
a. Embryo
b. Ovule
c. Endosperm
d. Embryo sac

Answer 1

Hint: The megaspore undergoes multiple karyokinesis and reaches the eight nucleate stage. Among these eight nuclei, one functions as the egg nuclei that fuses with the male gamete to produce zygote.

Complete answer:
There are two types of processes occurring in the angiosperms or the flowering plants. These processes are known as megasporogenesis and megagametogenesis. Megasporogenesis is the formation of the megaspore in the nucleus or the megasporangium. Megagametogenesis can be defined as the development of the megaspore into the embryo sac.

During the process of reproduction in angiosperms, the male gametophyte or microspores reach mega sporophyte. It then reaches the ovule through a pollen tube. Inside the ovule, one male gamete fuses with an egg of embryo sac and another male gamete fuses with a secondary nucleus. This is called megasporogenesis.

After megasporogenesis, the megaspore further develops into the female gametophyte or the embryo sac. The formation of embryo sac occurs through a process called megagametogenesis. This results in the development of a seven cell embryo sac, which consists of one central cell, two synergid cells, one egg cell and three antipodal cells.

The functional megaspore in angiosperm develops into an embryo sac.
So, the option d) Embryo sac, is correct.

Additional information:
The most common type of embryo development in angiosperms is monosporic type which is 8 nucleated and 7 celled. The female gametophyte of angiosperms, also termed as the embryo sac, contains only a few amounts of nuclei inside them. The cytoplasm which is associated directly with them is not partitioned by cell walls. One of these several nuclei present in the embryo sac serves as the egg during sexual reproduction.

Note: The process of megasporogenesis is when megasporocytes develop from megaspores. The cell undergoes meiosis and results in the formation of 4 haploid megaspore nuclei. Megagametogenesis is the process by which the embryo sac is formed. The embryo sac typically has eight nuclei in them.