- A Diploid sporophytic tissue of the pistil acting largely alone, without requiring much input from the pollen grain itself directly during normal conditions
- B Haploid pollen S-gene product interacting with pistil S-gene product; both encoded by multiallelic S-locus (e.g., RNase-based in Solanaceae)
- C The diploid seed coat tissue alone, acting mostly independently of any pollen-pistil molecular signaling interaction happening as generally observed
- D Epigenetic chromatin marks alone, occurring with little underlying genetic S-locus sequence ever being involved in practice in typical laboratory settings
Correct answer: B. Haploid pollen S-gene product interacting with pistil S-gene product; both encoded by multiallelic S-locus (e.g., RNase-based in Solanaceae)
Explanation: GSI: pollen S-allele product determines incompatibility. In Solanaceae: S-RNase (pistil) degrades RNA in incompatible pollen tubes. In Papaveraceae: Ca2+ signaling inhibits pollen tube growth.
Concept context
Flower structure, pollination, double fertilization, and seed/fruit development — the highest-scoring Class 12 biology chapter in NEET.
Read the full Sexual Reproduction in Flowering Plants notes →