Module: | Double Fertilization & Endosperm
Q75: Consider the following statements regarding exceptions to standard endosperm ploidy:
1. While typical angiosperm endosperm is triploid, species within the genus Oenothera (evening primrose) possess a diploid (2n) endosperm.
2. This diploid condition in Oenothera results causally from the fusion of a single male gamete with only one polar nucleus present in the central cell.
3. In stark contrast, all gymnosperms produce a heavily polyploid endosperm, typically pentaploid (5n), due to the fusion of five central nuclei prior to fertilization.
Which of the above statements is/are correct?
2. This diploid condition in Oenothera results causally from the fusion of a single male gamete with only one polar nucleus present in the central cell.
3. In stark contrast, all gymnosperms produce a heavily polyploid endosperm, typically pentaploid (5n), due to the fusion of five central nuclei prior to fertilization.
Which of the above statements is/are correct?
✅ Correct Answer: A
The correct option is A. Statements 1 and 2 are correct, whereas Statement 3 is entirely incorrect.
In the standard Polygonum type of embryo sac, two polar nuclei fuse with one male gamete to form a triploid (3n) endosperm.
However, botanical exceptions are frequently tested.
Oenothera exhibits a specialized 4-nucleate embryo sac containing only one synergid, one egg, and crucially, only a single polar nucleus in the central cell (with no antipodals). When double fertilization occurs, the fusion of one haploid male gamete with this single haploid polar nucleus naturally yields a diploid (2n) endosperm.
Statement 3 is a recurring pedagogical trap.
Gymnosperms do not undergo double fertilization, and their "endosperm" is actually the pre-fertilization female gametophyte tissue.
Therefore, the gymnosperm endosperm is strictly and universally haploid (n), never pentaploid.
In the standard Polygonum type of embryo sac, two polar nuclei fuse with one male gamete to form a triploid (3n) endosperm.
However, botanical exceptions are frequently tested.
Oenothera exhibits a specialized 4-nucleate embryo sac containing only one synergid, one egg, and crucially, only a single polar nucleus in the central cell (with no antipodals). When double fertilization occurs, the fusion of one haploid male gamete with this single haploid polar nucleus naturally yields a diploid (2n) endosperm.
Statement 3 is a recurring pedagogical trap.
Gymnosperms do not undergo double fertilization, and their "endosperm" is actually the pre-fertilization female gametophyte tissue.
Therefore, the gymnosperm endosperm is strictly and universally haploid (n), never pentaploid.