Apomixis and Polyembryony in Flowering Plants: NEET Biology Notes & Examples
Welcome to Grip the Biology , your premier destination for high-quality, NCERT-aligned medical entrance preparation. We take pride in delivering content that doesn't just mirror textbooks but decodes them. This guide on Sexual Reproduction of Flowering plants is meticulously crafted to meet the rigorous standards of the NTA NEET-UG syllabus, focusing exclusively on the core concepts that matter most."
Before exploring the Reproductive details of the Apomixis and Polyembryony in Flowering Plants: NEET Biology Notes & Examples ensure you have reviewed our previous guide on True, False & Parthenocarpic Fruits: High-Yield NEET Guide (NCERT Class 12 )to understand the reproductive context of flowering plants (Angiosperms) in the NEET journey."
Table of Contents
- Introduction to Special Modes of Reproduction
- What is Apomixis? (Definition & Meaning)
- Mechanism of Apomixis
- Types of Apomixis (Recurrent, Non-recurrent, Adventive)
- Importance and Applications of Apomixis in Agriculture
- Why Hybrid Seed Industry Needs Apomixis?
- What is Polyembryony? (Definition & Discovery)
- Causes of Polyembryony
- Key Examples of Apomixis and Polyembryony (Must-Know for NEET)
- Comparison Table: Apomixis vs. Polyembryony
- NEET high yield MCQs
Introduction to Special Modes of Reproduction
- In angiosperms (flowering plants), sexual reproduction typically involves two main processes Syngamy (the fusion of male and female gametes) and Meiosis (reduction division to form haploid gametes).
- These standard process leads to genetic variation and the formation of a normal diploid zygote, which develops into a seed.
- However, nature always has fascinating exceptions! Some flowering plants have evolved special modes of reproduction that bypass the usual pathway of fertilization or embryo development, yet they successfully mimic sexual reproduction by producing seeds.
- These alternative pathways are crucial adaptations for survival and reproduction under specific environmental conditions.
- In the NEET syllabus, the two most important special modes of reproduction you need to master are:
- Apomixis: A mechanism where seeds are formed without fertilization. It mimics sexual reproduction but is actually a form of asexual reproduction.
- Polyembryony: A phenomenon where a single seed contains more than one embryo.
Why do plants choose these special modes
- They allow plants to replicate high-yielding maternal traits exactly, without the genetic shuffling that happens during meiosis and Fertilization.
- These bypass the complex process of pollination and fertilization saves significant metabolic energy for the plant.
What is Apomixis? (Definition & Meaning)
- The word Apomixis is derived from two Greek words: Apo meaning "away from" and mixis meaning "mixing or mingling."
- Apomixis is a special form of asexual reproduction in flowering plants that mimics sexual reproduction but produces seeds without fertilization.
- Since there is no fusion of male and female gametes, the resulting embryo and seed are genetically identical to the maternal parent (clones).
- NEET Target Example: Apomixis is commonly seen in plants belonging to the families Asteraceae (sunflower family) and Poaceae (grasses).
💡Related study to understand about the Development of Endosperm & Embryo: Monocot vs Dicot Structure (NEET Biology)
Mechanism of Apomixis
- In normal sexual reproduction, a diploid megaspore mother cell undergoes meiosis to form a haploid egg cell, which is then fertilized by a sperm cell to form a diploid zygote.
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| Mechanisms of Apomixis |
- In Apomixis, this standard pathway is modified through three main cellular mechanisms:
- Bypassing Meiosis or Apomeiosis: The megaspore mother cell fails to undergo meiosis or undergoes abnormal mitosis, resulting in the formation of a diploid (2n) embryo sac.
- Parthenogenesis: The diploid egg cell inside the unreduced embryo sac develops directly into an embryo without fertilization by a male gamete.
- Independent Endosperm Development: In many apomictic plants, the endosperm (which provides nutrition to the embryo) develops autonomously without triple fusion, or via central cell fertilization (pseudogamy).
💡 Types of Apomixis ( Not aligned with NEET Syllabus)
📝 Recurrent Apomixis: The Megaspore Mother Cell does not undergo meiosis (reduction division) and directly forms a diploid (2n) embryo sac. The diploid egg cell then develops into an embryo without fertilization.
📝 Adventive Embryony (NCERT Special): The embryo does not develop from the cells of the embryo sac. Instead, diploid sporophytic cells surrounding the embryo sac—such as the Nucellus or Integuments—start dividing, protrude into the embryo sac, and develop into embryos.
Examples: Citrus and Mango.
📝Non-Recurrent Apomixis: Normal meiosis takes place, forming a haploid (n) embryo sac. However, the haploid egg cell develops into an embryo directly without fertilization (Haploid Parthenogenesis).
Importance and Applications of Apomixis in Agriculture
- Hybrid varieties of several of our food and vegetable crops are being extensively cultivated because they tremendously increase productivity and crop yield.
- However, using hybrid seeds comes with a major challenge for farmers.
Why Hybrid Seed Industry Needs Apomixis?
- There are various reasons to need Apomixis in hybrid seed industry :
The Problem of Segregation of Characters:
- If a farmer harvests seeds from a hybrid crop and sows them next year, the characters or traits in the progeny will segregate (separate) due to sexual reproduction.
- As a result, the offspring will lose the high-yielding hybrid efficiency, and the crop quality will drop.
The High Cost of Hybrid Seeds:
- Because of character segregation, farmers cannot reuse the seeds from their current harvest.
- They are forced to buy expensive new hybrid seeds every single year, which increases the financial burden on poor farmers.
The Apomixis Solution (The Ultimate Fix):
- If these high-yielding hybrids are genetically converted into apomicts, there will be no segregation of characters in the progeny.
- Because apomixis is a form of cloning (asexual reproduction via seeds), meaning the offspring will be exact genetic copies of the high-performing hybrid parent.
The Benefit:
- Farmers can keep using the hybrid seeds raised from their own harvest year after year to grow new crops.
- They will never need to buy expensive commercial hybrid seeds every season.
💡Related study to understand about the Pollen-Pistil Interaction & Double Fertilization: NEET Biology Master Guide
What is Polyembryony?
- Polyembryony is a phenomenon in which a single seed contains more than one embryo during its development.
- It was first observed and described by the famous scientist Antoni van Leeuwenhoek in 1719 in Citrus seeds.
💡NCERT Core Concept:
📝In many Citrus (orange, lemon) and Mango varieties, some of the nuclear cells surrounding the embryo sac start dividing, protrude into the embryo sac, and develop into embryos.
📝In many Citrus (orange, lemon) and Mango varieties, some of the nuclear cells surrounding the embryo sac start dividing, protrude into the embryo sac, and develop into embryos.
📝In such species, each ovule contains many embryos, leading to polyembryony.
Causes of Polyembryony
- Polyembryony can occur due to various cellular anomalies during seed development. The primary causes include:
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| Mechanism of Polyembrony |
Cleavage of the Zygote (Cleavage Polyembryony):
- The initial zygote or proembryo splits or divides into multiple units, and each unit independently develops into a fully formed embryo.
Development from Synergids or Antipodals:
- Cells other than the egg cell inside the embryo sac get fertilized or stimulated to divide directly into an embryo.
Proliferation of Nucellar Cells (Adventive Embryony):
- As highlighted in NCERT, maternal tissue like the nucellus or integuments actively undergoes mitosis, pushes inside the embryo sac, and forms additional embryos.
Comparison Table: Apomixis vs. Polyembryony
Key Examples of Apomixis and Polyembryony (Must-Know for NEET)
- To score full marks in NEET statement-based or match-the-following questions, you must memorise these specific examples. These are frequently repeated in previous years' questions (PYQs).
- In these plants, seeds are produced directly without the fusion of gametes.
- Asteraceae Family Includes flowering plants like sunflowers and dandelions.
- Poaceae Family Includes various species of grasses.
- Parthenium (Carrot Grass) is A well-known weed that shows regular apomictic seed development.
Core Examples of Polyembryony
- In these plants, a single seed contains multiple embryos during development:
- Citrus Fruits: Oranges, Lemons, and Limes (classic examples where nucellar embryony leads to multiple embryos).
- Mango (Mangifera indica): Certain traditional varieties consistently exhibit multiple embryos per seed.
- Gymnosperms (e.g., Pinus): Though not an angiosperm, Pinus is a very famous example of cleavage polyembryony often asked in NEET.
To understand the detail information about the Male Reproductive Structure in Flowering Plants: NEET Biology Notes read my next detailed guide
🎯 NEET MULTIPLE CHOICE QUESTIONS
🔥 100% CHALLENGE
"Questions yahi se aayega... taiyari jeet ki!"
1. Which one of the following phenomena is type of asexual reproduction but mimics to sexual reproduction.
A. Polyembryony
B. Apomixis
C. Syngamy
D. Parthenocarpy
Answer : B
2. Apomixis refer to development of
A. Seed without process of pollination.
B. fruit without the process of fertilisation.
C. Seed without the process of fertilisation.
D fruit without the process of pollination.
Answer: C
3. Apomixis can be seen in member of which of the following family.
A. Leguminoseae
B. Rosaceae
C. Solanaceae
D. Asteraceae
Answer : D
4. To develop apomictic seed, diploid egg cell is formed...........and develop in to embryo .......
A. Without reduction divison, With fertilization
B. With reduction divison, without fertilization.
C. With reduction divison, with fertilization
D. Without reduction divison, without fertilization
Answer : D
5. Which one of the following statement is correct.
A. Apomixis is development of fruit without the fertilization.
B. Members of Rosaceae develop apomictic seed.
C. Grasses exhibit the apomixis.
D. Apomictic seed are useless and no have importance in agriculture.
Answer : C
6. Occurrence of more than one in a seed is referred as
A. Polygamy
B.Polyandry
C.Protandry
D.None of the above
Answer : D
7. Which of the following cells around the embryo sac are protruded and and develop into many embryo.
A. Nuceller cell
B. Funicle cell
C. Chalazal cell
D. All of the above
Answer : A
8. Polyembryony can be seen in
A. Citrus and Mango
B. Grapes and Apple
C. Apple and Pear
D. Mango and pear
Answer : A
9. Which one of the following statement is correct about the polyembryony.
A. It has multiple embryo in each ovule.
B. Egg cell is not involved in formation of multiple embryo.
C. It can be seen in orchid and Grasses.
D. It mimics sexual reproduction.
Answer : A
10. Match the list
A. Asteraceae 1. Apomixis
B. Citrus 2. Polyembryony
C. Mango
D. Grasses
A B C D
A. 1 2 1 2
B. 2 2 1 1
C. 1 2 2 1
D. 2 1 1 2
Answer: C
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