A male plant with a diploid chromosome number of 16 is crossed with a female plant that is tetraploid ( 4n = 32 ). What will be the exact number of chromosomes in the zygote and the primary endosperm nucleus (PEN) of the resulting seed, respectively?

Step-by-step solution

The ploidy of the gametes depends on the ploidy of the parent plant. The male plant is diploid ( 2n = 16 ), so its male gametes will be haploid ( n = 8 ). The female plant is tetraploid ( 4n = 32 ), so its gametes and the nuclei of the embryo sac will be diploid ( 2n = 16 ). Thus, the egg cell has 16 chromosomes, and the central cell contains two polar nuclei, each with 16 chromosomes. During syngamy, one male gamete fuses with the egg cell to form the zygote: Zygote = Male gamete ( 8 ) + Egg cell ( 16 ) = 24 chrom