Question

Chalazogamy is characteristics of
A. Casuarina
B. Betula
C. Cucurbita
D. Both (A) and (B)

Answer 1

Hint:In plant ovules, the chalaza is located opposite the micropyle opening of the integuments. It is the tissue where the integuments and nucellus are joined. Chalazogamy was first discovered in monoecious plants.

Complete answer:
A process of fertilization in which the pollen tube penetrates to the embryo sac through the tissue of the chalaza. Chalazogamy is found in Casuarina, Betula etc.

Additional information:
The gametes which participate in fertilisation of plants are called pollen (male) and egg (female) cell. In seed plants, after pollination, a pollen grain germinates and a pollen tube grows and penetrates into the ovule through a tiny pore called the micropyle. The sperms are transferred from the pollen through the pollen tube to the ovule.

Double fertilisation is the process in the angiosperms in which two sperm from each pollen tube fertilise the two cells in a female gametophyte (also called an embryo sac) that is inside an ovule. After the pollen tube enters the gametophyte, the pollen tube nucleus disintegrates and the two sperm cells are released i.e., one of the two sperm cells then fertilises the egg cell (at the bottom of the gametophyte), forming a diploid (2n) zygote. This is the point where fertilisation actually happens; pollination and fertilisation are two separate processes.

Hence, the correct answer is option (D) i.e., Casuarina & Betula.

Note:Pollen grains (1 vegetative cell+ 2 polar nuclei) travel from stigma, through the style (long tunnel), finally in the ovule (after breaking filiform apparatus).
i) If they reach in ovule through chalaza then, it is called chalazogamy.
ii) If they reach in ovule via integuments then, it is called mesogamy.
iii) If they reach in ovule via Micropyle then, it is called porogamy.