Question

What is the port of the entry of the pollen tube into an embryo sac of Capsella?
A. Oosphere
B. One of the synergids
C. One of the antipodal cells
D. None of the above

Answer 1

Hint: In angiosperms the fertilization occurs via the pollen tube within the embryo sac of the plant. Capsella is an angiospermous plant. Moreover, the pollen tube enters into the embryo sac only from the micropylar end.

Complete step by step answer: Capsella is an angiospermous plant. In angiosperms, the fertilization occurs by the pollen-pistil interaction. There is only one way for the pollen tube to enter the inside of the embryo sac, i.e., through the micropylar end.
-The filiform apparatus is found on the micropylar end. It secrets some chemicals that attract the pollen tube towards itself or the micropylar end. This is known as chemotropic growth.
-When the pollen tube reaches the micropylar end of the embryo sac, then the cell wall dissolves and only the cell membrane persists towards one end of the synergids. Due to this, the synergid has to dissolve.
-The content of the pollen tube then reaches the egg cell via the synergid. In this process, the synergid is destroyed. Two black spots are formed known as the X-bodies.
-Thus, the port of the entry of the pollen tube into an embryo sac of Capsella is one of the synergids.
Hence, the correct answer is option (B).

Note: There are three alternate ways by which a pollen tube can enter inside the ovule. These three ways are –
1. Porogamy – It is the most common method. In porogamy, the micropylar end receives the pollen tube.
2. Chalazogamy – In chalazogamy, the pollen tube enters the ovule through the chalazal end.
3. Mesogamy – In mesogamy, the pollen tube enters the ovule through the integuments near the funicle.
However, there is only one way for the pollen tube to enter the embryo sac. It is through the micropylar end.