In the majority of flowering plants, out of the four megaspores produced in the ovule, what is the typical ratio of one functional megaspore to degenerate megaspores?

Introduction / Context:
In angiosperms (flowering plants), the female gametophyte or embryo sac develops from a megaspore inside the ovule. Typically, one diploid megaspore mother cell undergoes meiosis to produce four haploid megaspores. However, not all of these megaspores survive or develop further. This question tests whether you know the usual pattern of functional and degenerate megaspores in the majority of flowering plants.

Given Data / Assumptions:

• A megaspore mother cell divides meiotically to form four megaspores.

• The question asks for the ratio of functional to degenerate megaspores.

• Options present different possible ratios such as 2:2, 1:3, 3:1, 4:0, and 0:4.

• We assume the most common type of embryo sac development (the Polygonum type) in angiosperms.

Concept / Approach:
In the majority of flowering plants, the common type of megasporogenesis and embryo sac development is the monosporic Polygonum type. Here, one megaspore mother cell (megasporocyte) undergoes meiosis to form a linear tetrad of four haploid megaspores. Out of these four, usually only one, the one at the chalazal end, remains functional. The other three megaspores degenerate. The single functional megaspore then undergoes mitotic divisions to form the mature embryo sac. Therefore, the typical ratio is one functional megaspore and three degenerate megaspores, that is 1:3.

Step-by-Step Solution:
Step 1: Recall that the megaspore mother cell in the ovule undergoes meiosis I and II to produce four haploid megaspores in a linear arrangement. Step 2: In the common Polygonum type, three of these megaspores, usually the ones towards the micropylar end, degenerate. Step 3: The remaining single megaspore at the chalazal end remains functional and enlarges. Step 4: This functional megaspore undergoes three rounds of mitosis to produce an eight nucleate, seven celled embryo sac. Step 5: Since only one megaspore survives out of four, the ratio of functional to degenerate megaspores is 1 functional and 3 degenerate. Step 6: Compare this with alternative patterns such as bisporic or tetrasporic developments, which are less common and still usually involve only one functional megaspore in the final embryo sac. Step 7: Therefore, the most widely correct answer for the majority of flowering plants is 1:3.

Verification / Alternative check:
Plant reproduction chapters in botany textbooks describe megasporogenesis and embryo sac formation in detail. The standard diagram for the Polygonum type clearly shows a tetrad of four megaspores followed by degeneration of three and survival of one. The text typically states that in most angiosperms, only one megaspore is functional and the others degenerate. This widely accepted description confirms that the functional to degenerate ratio is 1:3 in the majority of flowering plants.

Why Other Options Are Wrong:

2 functional : 2 degenerate: This would imply that two megaspores contribute to embryo sac formation, which is not the usual pattern in the common monosporic type.

3 functional : 1 degenerate: Suggests that three megaspores survive, which contradicts the standard description for most angiosperms.

4 functional : 0 degenerate: Means all four survive, which is not observed in typical embryo sac development.

0 functional : 4 degenerate: Would mean no embryo sac could form, which cannot support normal reproduction.

Common Pitfalls:
Students may confuse the number of megaspores formed with the number that remain functional. It is easy to remember that meiosis produces four megaspores but forget that only one usually survives. Another pitfall is mixing up different types of embryo sac development and assuming that multiple megaspores are always involved. For basic exams, focus on the Polygonum type where one functional megaspore and three degenerate megaspores is the standard pattern.

Final Answer:
In the majority of flowering plants, the ratio of functional to degenerate megaspores is 1 functional : 3 degenerate.