The hollow foliar structure enclosing the shoot apex in monocots is:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: D
Answer: Coleoptile
Explanation: Epicotyl has a shoot apex and a few leaf primordia enclosed in a hollow foliar structure, the coleoptile.
Seed dormancy is triggered by:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Reduction in water content and metabolic activity
Explanation: As the seed matures, its water content is reduced... The general metabolic activity of the embryo slows down. The embryo may enter a state of inactivity called dormancy.
A seed is essentially a:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Fertilised ovule
Explanation: In angiosperms, the seed is the final product of sexual reproduction. It is often described as a fertilised ovule.
The oldest viable seed, Lupinus arcticus, was excavated from:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Arctic Tundra
Explanation: The oldest is that of a lupine, Lupinus arcticus excavated from Arctic Tundra.
Parasitic species like Orobanche produce:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: Thousands of tiny seeds
Explanation: Similar is the case in fruits of some parasitic species such as Orobanche and Striga. (Referring to thousands of tiny seeds).
Apomixis is observed in species of:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Asteraceae and Grasses
Explanation: A few flowering plants such as some species of Asteraceae and grasses, have evolved a special mechanism... called apomixis.
In Citrus and Mango, polyembryony arises from:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: Nucellar cells protruding into embryo sac
Explanation: In many Citrus and Mango varieties some of the nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into the embryos.
Hybrid seeds have to be produced every year because:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Progeny segregate and do not maintain hybrid characters
Explanation: If the seeds collected from hybrids are sown, the plants in the progeny will segregate and do not maintain hybrid characters.
A typical microsporangium appears ________ in transverse section.
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: Near circular
Explanation: In a transverse section, a typical microsporangium appears near circular in outline.
Which layer of the microsporangium helps in dehiscence of anther?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: Outer three wall layers
Explanation: The outer three wall layers perform the function of protection and help in dehiscence of anther.