Module: | Embryo, Seed, Fruit & Apomixis
Q97: Consider the following statements regarding the phenomena of xenia and metaxenia:
1. Xenia refers to the direct and immediate observable effect of foreign pollen on the characteristics of the endosperm or seed.
2. Metaxenia refers to the physiological effect of pollen on the maternal tissues lying entirely outside the embryo sac, such as the fruit coat.
3. Both xenia and metaxenia are strictly observed in all gymnosperms to speed up the development of the naked seeds.
Which of the above statements is/are correct?
2. Metaxenia refers to the physiological effect of pollen on the maternal tissues lying entirely outside the embryo sac, such as the fruit coat.
3. Both xenia and metaxenia are strictly observed in all gymnosperms to speed up the development of the naked seeds.
Which of the above statements is/are correct?
✅ Correct Answer: A
The correct option is A. Statements 1 and 2 are correct, whereas Statement 3 is fundamentally incorrect.
In standard botany, the maternal plant usually dictates the physical traits of the seed and fruit.
However, in certain angiosperms, the male pollen exerts an immediate, visible influence.
Xenia (described by Focke in 1881) is the direct effect of pollen on the embryo sac structures, most famously causing color changes in the endosperm of maize kernels depending on the pollen source.
Metaxenia (described by Swingle in 1928) is an even more advanced chemical phenomenon where hormones produced by the hybrid embryo/endosperm diffuse outward and alter the size, shape, or ripening time of the purely maternal fruit tissues (e.g., in date palms). Statement 3 fails the evolutionary taxonomy test: because gymnosperms lack double fertilization, true endosperm, and ovaries (fruits), they are biologically incapable of exhibiting either xenia or metaxenia.
In standard botany, the maternal plant usually dictates the physical traits of the seed and fruit.
However, in certain angiosperms, the male pollen exerts an immediate, visible influence.
Xenia (described by Focke in 1881) is the direct effect of pollen on the embryo sac structures, most famously causing color changes in the endosperm of maize kernels depending on the pollen source.
Metaxenia (described by Swingle in 1928) is an even more advanced chemical phenomenon where hormones produced by the hybrid embryo/endosperm diffuse outward and alter the size, shape, or ripening time of the purely maternal fruit tissues (e.g., in date palms). Statement 3 fails the evolutionary taxonomy test: because gymnosperms lack double fertilization, true endosperm, and ovaries (fruits), they are biologically incapable of exhibiting either xenia or metaxenia.