Triple Fusion in Flowering Plants — NEET Biology

Correct answer: C — S1, S3, S4 and S6

Sexual reproduction in angiosperms involves a series of coordinated events including the formation of gametes, pollination, fertilisation, and post-fertilisation development. S1: In over 60% of angiosperms, pollen grains are shed at the 2-celled stage (vegetative and generative cell). In such cases, the generative cell divides mitotically to form two male gametes during pollen tube growth in the stigma. In the remaining species, the generative cell divides before pollen shedding (3-celled stage). Thus, statement S1 is correct. S2: The filiform apparatus is present at the micropylar tip of the synergids and plays an important role in guiding the pollen tubes into one of the synergids, not directly into the egg cell. The male gametes are discharged into the cytoplasm of the synergid. Therefore, statement S2 is incorrect. S3: Syngamy is one of the two fusion events during double fertilisation. It involves the fusion of one male gamete (haploid) with the egg cell (haploid), resulting in the formation of a diploid zygote. Thus, statement S3 is correct. S4: Triple fusion is the second fusion event, where the other male gamete (haploid) moves towards the two polar nuclei (each haploid) located in the central cell and fuses with them to produce a triploid Primary Endosperm Nucleus (PEN). Thus, statement S4 is correct. S5: The endosperm development precedes embryo development. While the endosperm provides nutrition to the developing embryo, it is not always completely consumed before seed maturation in all angiosperms. For example, in pea, groundnut, and beans, the endosperm is completely consumed, making them non-albuminous. However, in castor and coconut, endosperm persists in the mature seed (albuminous seeds). Therefore, statement S5 is incorrect. S6: Double fertilisation is a phenomenon unique to flowering plants, involving two fusion events: syngamy and triple fusion, which occur in the embryo sac. Thus, statement S6 is correct. Based on the analysis, statements S1, S3, S4, and S6 are correct. Option C correctly identifies the correct statements.