Sexual Reproduction in Flowering Plants Set-2

Q1. A flowering plant has somatic chromosome number $2n=14$. After normal double fertilization between gametes from two such plants, what will be the chromosome number in the zygote and in the primary endosperm nucleus respectively?

Q2. In a species with obligate double fertilization (Polygonum-type embryo sac), a pollen grain reaches the stigma but contains only one functional male gamete (the second sperm is absent). That single sperm fuses with the egg cell while the polar nuclei remain unfertilized. Which of the following outcomes is the most likely immediate consequence for seed development?

Q3. Consider gametophytic self-incompatibility (GSI). A pistil has genotype S1S2. Two pollen donors have genotypes P1: S1S3 and P2: S3S4. Assuming equal pollen numbers from each donor, which donor is expected to produce a higher proportion of compatible pollen grains on this pistil?

Q4. According to the endosperm balance theory, normal endosperm development usually requires a maternal:paternal genome ratio of $2:1$ in the primary endosperm nucleus. Which one of the following crosses is most likely to produce viable seeds based on this requirement?

Q5. An apomictic plant (somatic $2n=2x$) forms an unreduced embryo sac so that the egg cell is $2x$ and each polar nucleus is $2x$; embryony is autonomous (no fertilization of egg) but pseudogamy is required (pollen must fertilize polar nuclei). If this diploid apomict is pollinated by a normal diploid sexual pollen donor ($2n=2x$), what are the most likely chromosome constitutions of the embryo and the primary endosperm nucleus, and what is the genetic relationship of the embryo to the mother plant?

Q6. In a flowering plant with Polygonum-type embryo sac, a diploid ($2n$) pistillate plant is pollinated by pollen from a tetraploid ($4n$) donor. Assuming normal meiosis and double fertilization, the resulting embryo and endosperm ploidies will be, respectively:

Q7. In a species with gametophytic self-incompatibility (GSI), a pistil has genotype $S_1S_2$ and a pollen donor has genotype $S_2S_3$. Pollen grains from the donor are haploid $S_2$ or $S_3$. Which pollen grains will be compatible on the pistil?

Q8. In a diploid ($2n$) species, nondisjunction during microsporogenesis produced a microspore that carries one extra chromosome (so the sperm nuclei in that pollen are $n+1$ each). This pollen fertilizes a normal haploid egg ($n$) and a normal central cell (two polar nuclei, each $n$) of a diploid ovule. What will be the chromosome numbers of the embryo and the endosperm, respectively?

Q9. Statement I: Crosses where the paternal genome contribution to the endosperm is disproportionately higher than normal often produce non-viable seeds. Statement II: Endosperm development commonly requires a specific maternal:paternal genomic ratio (typically $2m:1p$) and genomic imprinting; deviation from this ratio disrupts endosperm formation. Choose the correct relationship between the two statements.

Q10. Due to meiotic failure an unreduced embryo sac is formed in a flowering plant: the egg cell is $2n$ and the central cell has two polar nuclei each $2n$ (central cell $4n$). Fertilization is by a normal haploid sperm ($n$) from a diploid pollen donor. What will be the ploidies of the embryo and endosperm, and what is the likely effect on seed viability given the typical maternal:paternal endosperm requirement?