Question

Which of the following has been observed for the first time by Treub?
(A) Entry of the pollen tube into the ovule through micropyle in Casuarina
(B) Entry of the pollen tube into the ovule through chalaza in Casuarina.
(C) Entry of the pollen tube into the ovule through the integuments.
(D) Formation of many pollen tubes from a single pollen grain in Hibiscus.

Answer 1

The pollen grain follows the three ways to reach the ovule. It passes through the pollen tube and enters the ovule by the micropyle, it enters the ovule through the chalaza tissue and it enters the ovule through the integumentary layers of the ovule.

Complete answer:
The pollen grains are the male reproductive cell and the eggs in the ovule are the female reproductive cell. In the sexual reproduction of the flowers, the pollen grain enters the pollen tube of the flowers. After that it flows through the pollen tube and reaches the ovule either by micropyle or by the chalaza or by the integumentary leaves.

If the pollen enters the ovule through the micropyle, it is called porogamy. If it enters through the chalaza it is called as the chalazogamy. If the pollen grains enter the ovule through the integumentary layers it is called as the mesogamy. Treub was the first one who found the entry of the pollen grain into the ovule through the chalaza in Casuarina.

Hence the correct answer is OPTION(B)

Note: The chalazogamy mainly occurred in the plants of the Betulaceae and the Juglandaceae. The mesogamy is also called the partial chalazogamy since it occurs midway between the chalaza tissues and the micropyle hole. This occurred in Ulmus.