Question

Write a short note on polyembryony.

Hint:

Think about a seed that ends up with more than one embryo, and where the extra ones come from.

Answer 1

Step 1: Understanding the Concept:
Normally, one fertilised egg (zygote) inside one ovule develops into exactly one embryo. Polyembryony is the occurrence of more than one embryo inside a single seed.

Step 2: Explain how it happens.
It can arise in more than one way: sometimes more than one archesporial cell or nucellar cell starts forming an embryo-like structure without fertilisation (adventive embryony), and sometimes the true zygotic embryo splits early into more than one embryo.

Step 3: Give an example and its use.
It is common in citrus fruits (like orange), where nucellar cells around the embryo sac develop into extra embryos alongside the normal zygotic one. This trait is used commercially, since nucellar embryos are genetically identical to the mother plant, giving true to type saplings.

Final Answer:
Polyembryony is the presence of more than one embryo in a single seed, seen well in citrus, and it is valuable in horticulture for producing genetically uniform, disease free planting material.