Which pollination brings genetically different pollen to the stigma?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: Xenogamy
Explanation: Xenogamy... This is the only type of pollination which during pollination brings genetically different types of pollen grains to the stigma.
Corn cob tassels are:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Stigma and style
Explanation: The ears you see are nothing but the stigma and style which wave in the wind.
Pollination in Vallisneria occurs:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: On water surface
Explanation: In Vallisneria, the female flower reach the surface of water... pollen grains are released on to the surface of water.
Pollination in Seagrasses (Zostera) occurs:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Submerged in water
Explanation: In... seagrasses, female flowers remain submerged in water and the pollen grains are released inside the water.
Which of the following statements regarding the wall layers of a typical microsporangium is correct?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: A
Answer: The outer three layers perform the function of protection and dehiscence.
Explanation: A typical microsporangium is surrounded by four wall layers: the epidermis, endothecium, middle layers, and tapetum. The outer three wall layers perform the function of protection and help in dehiscence of anther to release the pollen. The innermost layer is the tapetum which nourishes the developing pollen grains.
Identify the correct sequence of cells/structures from the outermost to the innermost part of a transverse section of a young anther.
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Epidermis -> Endothecium -> Middle Layers -> Tapetum -> Sporogenous Tissue
Explanation: The wall layers from outside to inside are epidermis, endothecium, middle layers, and tapetum. The center is occupied by sporogenous tissue.
Regarding the ploidy levels of the cells involved in microsporogenesis, which of the following is correct?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Pollen Mother Cell (PMC) is diploid; Microspore tetrads are haploid.
Explanation: The cells of the sporogenous tissue (PMCs) are diploid (2n) and undergo meiosis to form microspore tetrads, which are haploid (n).
Which distinct feature allows pollen grains to be preserved as fossils for long periods?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: The presence of sporopollenin in the exine.
Explanation: The hard outer layer called the exine is made up of sporopollenin, which is one of the most resistant organic materials known. It withstands high temperatures, strong acids, and alkalis, allowing pollen to be preserved as fossils.
In the majority of angiosperms (over 60%), pollen grains are shed at the 2-celled stage. What constitutes these two cells?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: One vegetative cell and one generative cell.
Explanation: In over 60 percent of angiosperms, pollen grains are shed at the 2-celled stage, comprising a large vegetative cell and a small generative cell. In the remaining species, the generative cell divides to form two male gametes before shedding (3-celled stage).
Which of the following statements about the vegetative cell of a pollen grain is true?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: It is bigger, has abundant food reserve and a large irregularly shaped nucleus.
Explanation: The vegetative cell is bigger, has abundant food reserve, and a large irregularly shaped nucleus. The generative cell is small, spindle-shaped, and floats in the cytoplasm of the vegetative cell.