Question

In the fertilization process of Angiosperms, the pollen grain is usually shed at which stage?

• A. 1-celled stage
• B. 2-celled stage (Vegetative and Generative)
• C. 4-celled stage
• D. No specific stage

Hint:

Remember the statistic:
- $>60\%$ of angiosperms shed pollen at the 2-celled stage.
- $<40\%$ of angiosperms shed pollen at the 3-celled stage (where the generative cell has already divided into two male gametes).

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify the typical cellular developmental stage at which pollen grains are released (shed) from the anther in the majority of flowering plants (Angiosperms).

Step 2: Detailed Explanation:

• In angiosperms, microspores develop within the anther to form pollen grains, which represent the male gametophyte.

• During this development, the protoplast of the micropore undergoes asymmetric mitotic division to produce two unequal cells:
- Vegetative Cell: This is the larger cell, containing abundant food reserves and a large, irregularly shaped nucleus. It is responsible for pollen tube growth.
- Generative Cell: This is the smaller, spindle-shaped cell with dense cytoplasm and a nucleus, which floats inside the cytoplasm of the vegetative cell. It is responsible for producing the male gametes.

• In over $60\%$ of all angiospermic families, pollen grains are shed from the anthers at this specific 2-celled stage (Vegetative and Generative).

• In the remaining plants (less than $40\%$), the generative cell undergoes a second mitotic division to form two male gametes before the pollen grains are shed, meaning they are released at the 3-celled stage.

• Therefore, the most common or usual shedding stage across angiosperms is the 2-celled stage.

Step 3: Final Answer:
In most angiosperms, pollen grains are shed at the 2-celled stage (containing a vegetative cell and a generative cell).