Which one of the following types of pollination brings genetically different types of pollen grains to the stigma?

Core Logic

The process of formation of microspores from a pollen mother cell (PMC) through meiosis is called microsporogenesis.

The developmental sequence is:

• Sporogenous tissue (B) fills the center of the young microsporangium.
• As the anther develops, the sporogenous cells differentiate into Pollen Mother Cells (PMCs) or microspore mother cells (D).
• Each PMC undergoes meiosis to form a cluster of four haploid cells called a Microspore tetrad (A).
• As the anthers mature and dehydrate, the microspores dissociate from each other and develop into Pollen grains (C).

Step 1: Final Conclusion

The correct sequence is B → D → A → C.

Pattern Recognition

Tissue -> Mother Cell -> Tetrad (intermediate) -> Pollen Grain (mature product). This is a logical biological progression from undifferentiated mass to individual mature gametophytes.

Chapter Mix

Class 12 Biology: Sexual Reproduction in Flowering Plants

Core Logic

Let's determine the ploidy of each cell type in angiosperms:

• Synergid: Haploid (n), part of the unfertilized egg apparatus.
• Zygote: Diploid (2n), formed by fusion of a male gamete (n) and the egg cell (n).
• Central cell: Initially binucleate (n+n) forming a secondary nucleus (2n) before fertilization.
• Primary endosperm cell (PEC): Formed when the second male gamete (n) fuses with the secondary nucleus (2n). Therefore, it is Triploid (3n).

Step 1: Final Conclusion

The Primary endosperm cell is the triploid cell.

Pattern Recognition

Double fertilization in angiosperms: syngamy produces a 2n zygote, triple fusion produces a 3n primary endosperm nucleus/cell (PEC).

Chapter Mix

Class 12 Biology: Sexual Reproduction in Flowering Plants