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Step-by-Step Explanation
1. Introduction to Ovule Types
In flowering plants (angiosperms), the ovule is the structure that develops into the seed after fertilization. Ovules can be classified based on the orientation of the nucellus, funiculus (the stalk attaching the ovule to the ovary), and micropyle (the opening through which pollen tube enters).
2. Understanding Amphitropous Ovule
The specific feature of an amphitropous ovule is that both the body of the ovule and the embryo sac are curved. The curvature leads to a
horse-shoe or U-shaped orientation of the embryo sac. As a result, the micropyle and the funiculus come to lie closer to each other.
A well-known family that shows amphitropous ovules is Papaveraceae.
3. Contrasting with Other Ovule Types
Circinotropous: The funicle in this type is extremely long and often coils around the ovule. An example is found in
Opuntia (a genus of cacti).
Atropous (Orthotropous): The ovule lies straight so that the micropyle, nucellus, and funiculus are aligned in a straight line.
Anatropous: The body of the ovule is inverted during development, bringing the micropyle near the funiculus, but the embryo sac
itself does not assume a horse-shoe shape.
4. Conclusion
The defining characteristic of an amphitropous ovule is the curved embryo sac, which becomes horse-shoe shaped, making the micropyle
and funiculus lie close to one another. Therefore, the correct answer is Amphitropous.
