Question

In porogamy, the pollen tube enters the ovule through
a. Funicle
b. Chalaza
c. Micropyle
d. Integuments

Answer 1

Hint: Ovule is the female reproductive part of the flower. It mainly consists of three parts that are integument, nucellus and the female gametophyte. Female gametophyte or ovule is formed from haploid megaspore. Fusion of male gametes (pollen grains) and female gametes (ovule) results in the formation of zygote. Pollen grains reach the ovule through the pollen tube through different openings. It can be porogamy, mesogamy or chalazogamy.

Complete answer:
> Gynoecium contains ovule inside the flower. One ovary releases one or more ovules. Ovules fuse with pollen grains by the process of fertilization. Ovule results in the ultimate formation of seeds while ovary develops into fruit. Parts of the ovule are funicles (stalks) through which ovules are attached to the placenta.

> Micropyle end of the ovule is inverted facing the placenta due to this orientation it is called anatropous (micropyle in downward position). Initially ovules are diploid (megasporocyte) which undergoes meiosis and produce haploid female gametophyte or megagametophyte. After fertilization zygote is formed which forms embryos and then seeds. Endosperm provides nourishment to the young sporophyte. When the pollen tube enters the ovule through the micropyle end it is called porogamy which is common in angiosperms.

> Protective layer of cells surrounding the ovule is known as integument. Generally gymnosperms have one integument while angiosperms have two integuments. After fertilization it develops into a seed coat. It retains an opening at the apex that is micropyle. Pollen tubes may also enter through integuments or through funiculus and this process is called mesogamy.

> Chalazal end is the opposite end to the micropyle where nucleus joined to the integuments. If the pollen tube enters through the chalazal end it is termed as chalazogamy. It is most commonly observed in chalazogamous plants.

As we have discussed above we can say that porogamy occurs at micropyle.
Hence, the correct answer is option (C).

Note: After entry of male gametes through pollen tube pollen grains fuses with ovule and forms zygote. Double fertilization is also seen in many cases if the pollen grains fuses with polar nuclei and egg cell triploids are formed and the process is called double fertilization. Formation of polyploids results in the formation of endosperms. Depending on the number of megaspores flowering plants may be described as monosporic, bisporic, or tetrasporic.