Which plant species, introduced into India as a contaminant with imported wheat, is ubiquitous and known to cause pollen allergy?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Parthenium hysterophorus
Explanation: Parthenium or carrot grass came into India as a contaminant with imported wheat, has become ubiquitous in occurrence, and causes pollen allergy.
For crop breeding programmes, pollen grains can be stored for years in liquid nitrogen at what temperature?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: -196 degrees C
Explanation: It is possible to store pollen grains of a large number of species for years in liquid nitrogen (-196 degrees C) for use in pollen banks.
Select the correct association of the part of the pistil and its function/description.
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: D
Answer: Placenta: Located inside the ovarian cavity (locule) from which megasporangia arise.
Explanation: The placenta is located inside the ovarian cavity (locule). Arising from the placenta are the megasporangia, commonly called ovules. The stigma is the landing platform; the style is the slender part; the ovary is the basal bulged part.
A multicarpellary, apocarpous gynoecium is characteristic of which of the following plants?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Michelia
Explanation: The pistils may be free (apocarpous) as in Michelia. In Papaver, the pistils are fused together (syncarpous).
In a typical anatropous ovule, the region where the body of the ovule fuses with the funicle is called:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: Hilum
Explanation: The body of the ovule fuses with the funicle in the region called hilum. Thus, hilum represents the junction between ovule and funicle.
Which cells within the ovule are described as having abundant reserve food materials?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Cells of the Nucellus
Explanation: Enclosed within the integuments is a mass of cells called the nucellus. Cells of the nucellus have abundant reserve food materials.
During monosporic development of the female gametophyte, what happens to the four megaspores formed from the MMC?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: One remains functional (chalazal end usually) while three degenerate.
Explanation: In a majority of flowering plants, one of the megaspores is functional while the other three degenerate. Only the functional megaspore develops into the female gametophyte.
The mitotic divisions leading to the formation of the embryo sac nucleus are described as "strictly free nuclear". What does this imply?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Nuclear divisions are not followed immediately by cell wall formation.
Explanation: These mitotic divisions are strictly free nuclear, that is, nuclear divisions are not followed immediately by cell wall formation. Cell walls are laid down only after the 8-nucleate stage.
Which of the following correctly describes the cellular organization of a mature angiosperm embryo sac?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: 7 cells, 8 nuclei.
Explanation: A typical angiosperm embryo sac, at maturity, though 8-nucleate is 7-celled. It contains 3 antipodals, 2 synergids, 1 egg cell, and 1 central cell (with 2 polar nuclei).
The filiform apparatus is a specialized cellular thickening located in which part of the embryo sac, and what is its function?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: In the synergids; to guide the pollen tube entry.
Explanation: The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid.