Biology · Sexual Reproduction in Flowering Plants · NEET
Polyembryony means the presence of more than one embryo in a single seed. In many Citrus and Mango varieties, the nucellar cells around the embryo sac divide, push into the embryo sac, and grow into extra embryos. Memory hook: cut open an orange seed and you may see many little embryos of different sizes — "one seed, many babies."
In many Citrus and Mango seeds, diploid nucellar cells of the mother plant divide and grow into extra embryos inside the embryo sac. Because there is no meiosis and no fertilisation, these nucellar embryos are clones of the parent, and the seed ends up with more than one embryo (polyembryony).
Your doubts, answered
Is polyembryony the same as apomixis?
No, but they are linked. Apomixis is seed formation without fertilisation. Polyembryony simply means more than one embryo is present in a seed. In Citrus and Mango, apomixis happens because nucellar cells grow into extra embryos, so the same seed also shows polyembryony. But polyembryony can also form by other routes, so the two terms are not identical.
Where do the extra embryos in Citrus and Mango seeds come from?
They come from the nucellus. In many Citrus and Mango varieties, some nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac, and develop into embryos. These are called nucellar embryos. Because the nucellus is diploid sporophyte tissue of the mother plant, these embryos are formed without fertilisation.
Are polyembryony (apomictic) embryos clones of the mother plant?
Yes, the nucellar (apomictic) embryos are clones. They arise from the mother plant's own nucellar cells without meiosis and without fertilisation, so they carry exactly the same genes as the parent. This is why apomixis is very useful in agriculture: hybrid seed can keep its qualities generation after generation.
How is polyembryony different from double fertilisation?
Double fertilisation is a normal sexual event: one male gamete fuses with the egg (syngamy) and the other fuses with the polar nuclei (triple fusion), giving one embryo plus endosperm. Polyembryony is about the number of embryos in the seed being more than one, often because extra embryos form from nucellar cells without any fertilisation.
⚠️ The NEET trap ✗ All embryos in a polyembryonic Citrus seed are formed from fertilised eggs and are genetically different from the mother. ✓ In Citrus and Mango, most extra embryos are nucellar embryos formed from diploid nucellus cells without fertilisation, so they are clones of the mother plant. 🧠 NEET links polyembryony to apomixis. If embryos come from the nucellus, there is no meiosis and no fertilisation, so the embryos are genetically identical to the parent.
Real NEET questions
2016
Seed formation without fertilization in flowering plants involves the process of:
A · Sporulation
B · Budding
C · Somatic hybridization
D · Apomixis ✓
Solution: Production of seeds without fertilisation is apomixis, a form of asexual reproduction that mimics sexual reproduction, seen in some Asteraceae and grasses and in many Citrus and Mango varieties. In these, nucellar cells develop into extra embryos, which is why such seeds show polyembryony. Sporulation and budding do not form seeds; somatic hybridisation is cell fusion in tissue culture.
Solved Sexual Reproduction in Flowering Plants NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Polyembryony is the occurrence of more than one embryo in a single seed. It is described in the NCERT chapter on Sexual Reproduction in Flowering Plants along with apomixis.
Give an example of a plant showing polyembryony.
Many varieties of Citrus (like orange) and Mango show polyembryony. If you squeeze orange seeds, you can see several embryos of different sizes and shapes.
What are nucellar embryos?
Nucellar embryos are extra embryos that form when some nucellar cells around the embryo sac divide, protrude into it, and grow into embryos. Because they form from mother-plant tissue without fertilisation, they are clones of the parent.
Why is polyembryony important in agriculture?
The nucellar embryos are genetically identical to the mother plant. This lets farmers keep the qualities of a good hybrid variety in the seed generation after generation, without the traits breaking up during sexual reproduction.
