Apomixis and Polyembryony
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Direct answer
Apomixis is a form of asexual reproduction that mimics sexual reproduction: flowering plants of families such as Asteraceae and grasses produce seeds without meiosis and without fusion of gametes, so the seedlings are genetic copies of the parent. Polyembryony is the presence of more than one embryo in a seed, classically in Citrus, where additional embryos often arise from the nucellus. Together they matter commercially, because introducing apomixis into hybrid crops would let farmers replant their own seeds year after year without losing hybrid vigour.
What you must remember
- Definition of apomixis: seed production that bypasses both meiosis and syngamy (fertilisation), so embryos develop asexually and the progeny resembles the parent exactly.
- The mask: apomixis mimics sexual reproduction because seeds and fruits still form — only the cytological events differ.
- Who does it: many species of Asteraceae (sunflower family) and grasses (Poaceae), the two families NCERT names.
- Why hybrids need it: conventional F1 hybrid seed must be bought afresh every season because progeny of saved seed segregates and loses hybrid characters; apomictic hybrids would breed true through seeds.
- Economics: apomixis would dramatically lower the cost of hybrid seed production and make it feasible for small farmers to save their own seed.
- Polyembryony: occurrence of more than one embryo within a single seed, the classic example being Citrus.
- Origin of extra embryos: in Citrus, cells of the nucellus surrounding the embryo sac develop into additional embryos alongside the sexual one.
Common confusion
Apomixis is not ordinary vegetative propagation — the plant reproduces through true seeds and fruits, which is why it imitates sex while skipping meiosis and fusion. Polyembryony, similarly, is not twinning in the animal sense; extra embryos arise from maternal nucellar tissue and are genetically identical to the mother plant, while the sexual embryo is not. Apomixis avoids segregation; that single sentence is the heart of every exam question on the topic.
Exam-focused takeaway
NEET-UG defines apomixis as asexual seed formation without meiosis and syngamy, asks for Asteraceae and grasses as the families, and links polyembryony with Citrus. Assertion-reason stems test that apomictic seeds conserve hybrid vigour and spare farmers the cost of fresh hybrid seed each year. Expect one-liners on how many embryos a polyembryonic seed contains and where the extra embryos come from.
Frequently asked questions
What is apomixis?
A special mechanism of asexual reproduction in which seeds form without meiosis and fertilisation, producing offspring genetically identical to the parent plant.
Which plant families commonly show apomixis?
Asteraceae and the grasses, in which many species reproduce apomictically.
What is polyembryony?
The presence of more than one embryo in a seed, classically seen in Citrus, where nucellar cells give rise to additional embryos.
Why is apomixis commercially valuable?
Because apomictic hybrid seeds do not segregate, farmers could save and reuse seeds while retaining hybrid vigour, cutting the yearly cost of buying fresh hybrid seed.
How does apomixis differ from vegetative propagation?
Apomixis produces seeds and fruits through reproductive structures, whereas vegetative propagation uses vegetative parts like stems, roots or leaves — apomixis mimics sex, vegetative propagation does not.