Which plant species, introduced into India as a contaminant with imported wheat, is ubiquitous and known to cause pollen allergy?
Parthenium or carrot grass came into India as a contaminant with imported wheat, has become ubiquitous in occurrence, and causes pollen allergy.
Question 212 of 501
📘 CLASS XII
For crop breeding programmes, pollen grains can be stored for years in liquid nitrogen at what temperature?
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.
Question 213 of 501
📘 CLASS XII
Select the correct association of the part of the pistil and its function/description.
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.
Question 214 of 501
📘 CLASS XII
A multicarpellary, apocarpous gynoecium is characteristic of which of the following plants?
The pistils may be free (apocarpous) as in Michelia. In Papaver, the pistils are fused together (syncarpous).
Question 215 of 501
📘 CLASS XII
In a typical anatropous ovule, the region where the body of the ovule fuses with the funicle is called:
The body of the ovule fuses with the funicle in the region called hilum. Thus, hilum represents the junction between ovule and funicle.
Question 216 of 501
📘 CLASS XII
Which cells within the ovule are described as having abundant reserve food materials?
Enclosed within the integuments is a mass of cells called the nucellus. Cells of the nucellus have abundant reserve food materials.
Question 217 of 501
📘 CLASS XII
During monosporic development of the female gametophyte, what happens to the four megaspores formed from the MMC?
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.
Question 218 of 501
📘 CLASS XII
The mitotic divisions leading to the formation of the embryo sac nucleus are described as "strictly free nuclear". What does this imply?
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.
Question 219 of 501
📘 CLASS XII
Which of the following correctly describes the cellular organization of a mature angiosperm embryo sac?
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).
Question 220 of 501
📘 CLASS XII
The filiform apparatus is a specialized cellular thickening located in which part of the embryo sac, and what is its function?
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.
