Question

Consider a diploid plant species where the cells in the epidermis (the outermost single cell layer) always divide in the anticlinal orientation. If one such cell within the central zone of the shoot apical meristem (SAM) spontaneously becomes tetraploid at the seedling stage, which one of the following cellular arrangements would be most likely observed if the meristem is examined at the adult stage?

• A. Only one tetraploid cell in the epidermis
• B. Many tetraploid cells in the epidermis
• C. All cells in the entire SAM tetraploid
• D. All cells in the entire SAM diploid

Hint:

When a tetraploid cell arises in a plant meristem, it typically proliferates and results in multiple tetraploid cells in the affected tissue, especially when divisions occur in an anticlinal orientation.

Answer 1

The Correct Option is B

In the given situation, a single cell in the epidermis of a diploid plant becomes tetraploid at the seedling stage. The key point here is that the cells in the epidermis divide in an anticlinal orientation, meaning that the division occurs perpendicular to the surface of the plant. When one of these epidermal cells becomes tetraploid, its daughter cells will also be tetraploid as they divide, leading to a clonal expansion of tetraploid cells in the epidermis. Therefore, we would expect many tetraploid cells to be present in the epidermis as a result of the clonal division of the initial tetraploid cell. Hence, statement (B) is correct.
- (A): If only one tetraploid cell were present in the epidermis, this would imply that the tetraploid cell did not divide or proliferate, which contradicts the scenario described in the question. Hence, statement (A) is incorrect.
- (C): The question specifically mentions that the tetraploid cell is in the epidermis, not the entire SAM (shoot apical meristem). Therefore, the entire SAM becoming tetraploid is unlikely. Hence, statement (C) is incorrect.
- (D): If all cells in the SAM were diploid, there would be no tetraploid cells present, which contradicts the assumption that one epidermal cell is tetraploid. Hence, statement (D) is incorrect.
Thus, the correct answer is (B), as many tetraploid cells in the epidermis would most likely be observed at the adult stage due to clonal proliferation.