Question

Describe polyembryony with an example.

Hint:

More than one embryo per seed, e.g. nucellar embryos in Citrus.

Answer 1

Step 1: Define polyembryony:
Polyembryony is the occurrence of more than one embryo in a single seed.

Step 2: Explain how it arises:
It commonly arises when, in addition to the zygotic embryo formed by normal fertilization, some of the surrounding nucellus (or sometimes integument) cells also start dividing and develop into additional embryos, without undergoing fertilization themselves (a form of apomixis).

Step 3: Give an example:
Citrus species (like orange) commonly show polyembryony, where multiple nucellar embryos develop alongside the zygotic embryo within the same seed, producing several genetically identical seedlings from one seed.

Final Answer:
Polyembryony is the presence of multiple embryos in one seed, commonly seen in Citrus, where extra nucellar embryos form alongside the normal zygotic embryo.