Question

Which one of the following is surrounded by a callose wall?

• A. male gamete
• B. egg
• C. pollen grain
• D. microspore mother cell.

Answer 1

The Correct Option is D

The question asks which one of the provided options is surrounded by a callose wall. The options given are:

• Male gamete
• Egg
• Pollen grain
• Microspore mother cell

Let's explore each option to determine the correct answer:

1. Male gamete: In plants, the male gametes are typically not surrounded by a callose wall. They are produced within the pollen grains, but the gametes themselves are not enclosed by a callose wall.
2. Egg: The egg cell in plants is not surrounded by a callose wall. It is part of the female gametophyte within the ovule, but callose does not generally encapsulate it.
3. Pollen grain: Pollen grains are derived from microspores. While the pollen grain wall may have callose in the initial stages of development (especially deposition during meiosis of the microspore mother cell), the mature pollen grain wall is primarily composed of sporopollenin, which provides structural toughness.
4. Microspore mother cell: Before the formation of pollen grains, microspore mother cells (also called pollen mother cells) undergo meiosis to form microspores. Initially, these microspore mother cells are surrounded by a callose wall, which provides protection during cell division. The degradation of callose marks the transition of microspores to mature pollen grains. Therefore, the microspore mother cell is the correct answer.

Thus, the correct answer is the microspore mother cell, as it is surrounded by a callose wall during its initial stages after meiosis.