Question

The process of double fertilization in angiosperms is correctly described by

• A. Two pollen grains land on each stigma; thus, two ovules are fertilized
• B. Two sperm cells produced by a single pollen grain fertilize two separate ovules, resulting in the formation of two seeds
• C. One sperm cell from a single pollen grain fertilizes an egg cell to form a diploid zygote, while a second sperm cell from the same pollen grain combines with two fused nuclei in the embryo sac, resulting in the formation of a triploid endosperm nucleus
• D. One sperm cell from a single pollen grain fertilizes an egg cell to form a haploid zygote, while a second sperm cell from the same pollen grain combines with a single nucleus in the embryo sac, resulting in the formation of a diploid endosperm nucleus
• E. Two sperm cells from a single pollen grain fertilize the same egg cell to double the chance that fertilization will be successful

Answer 1

The correct option is C One sperm cell from a single pollen grain fertilizes an egg cell to form a diploid zygote, while a second sperm cell from the same pollen grain combines with two fused nuclei in the embryo sac, resulting in the formation of a triploid endosperm nucleus

In flowering plants, the landing of pollen on stigma is followed by rupturing of exine and growth of intine as long slender pollen tube. Depending upon two or three-celled pollen grain, the pollen tube carries vegetative nucleus and a vermiform generative cell or a vegetative nucleus and two spindle-shaped male gametes. Pollen tube penetrates the stylar canal and enters the ovule through micropyle chalaza or integument followed by discharge of male gametes in the embryo sac. One male gamete fuses with egg nucleus (syngamy) to form the diploid embryo. And the other male gamete fuses with diploid secondary nucleus/central cell (triple fusion) to form triploid endosperm. Syngamy and triple fusion are collectively referred to as double fertilization which is a characteristic feature of angiosperms. Thus, the correct answer is option C.