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Difference Between Apomixis and Polyembryony

Difference Between Apomixis and Polyembryony

Irshad AnwarUpdated on 02 Jul 2025, 07:10 PM IST

Apomixis and Polyembryony are the two special types of Plant Reproduction. It involves the formation of multiple embryos without the fusion of gametes. The Difference between Apomixis and Polyembryony, in Apomixis, seeds are formed without fertilisation, with the new plant exactly like the parent. In Polyembryony, more than one embryo is formed inside a single seed, which means more than one plant can grow from it. Apomixis and Polyembryony are special cases that differ from normal Sexual Reproduction in Flowering Plants.

This Story also Contains

  1. What Is Apomixis?
  2. Characteristics Of Apomixis
  3. What Is Polyembryony?
  4. Characteristics Of Polyembryony
  5. Key Differences Between Apomixis And Polyembryony
  6. MCQs in Apomixis And Polyembryony
Difference Between Apomixis and Polyembryony
Difference Between Apomixis and Polyembryony

Fertilisation in Plants is an important step for seed formation, but Apomixis and Polyembryony are the exceptions. These form the seeds and embryos without typical fertilisation. This article includes the Difference between Apomixis and Polyembryony, Apomixis and Polyembryony characteristics, and some important MCQs on Apomixis and Polyembryony in Biology.

What Is Apomixis?

Apomixis is defined as the asexual method of production of seeds or embryos without fertilization. In this process, the embryo develops from a somatic cell or an unreduced female gametophyte, resulting in genetically identical offspring.

Commonly Asked Questions

Q: What role does meiosis play in apomixis?
A:
In apomixis, meiosis is often bypassed or altered. Instead of producing haploid gametes through meiosis, the plant produces diploid cells that develop into embryos without fertilization. This maintains the maternal plant's genetic makeup in the offspring.
Q: What is the evolutionary significance of apomixis?
A:
Apomixis can provide an evolutionary advantage by allowing successful genotypes to reproduce rapidly and colonize new areas. However, it can also limit a species' ability to adapt to changing environments due to reduced genetic variation.
Q: What is the relationship between apomixis and ploidy levels in plants?
A:
Apomixis is often associated with polyploidy (having multiple sets of chromosomes) in plants. Many apomictic species are polyploids, which may contribute to the genetic and physiological conditions necessary for apomictic reproduction.
Q: What are some challenges in studying apomixis in natural plant populations?
A:
Challenges in studying apomixis in natural populations include distinguishing between apomictic and sexual offspring, identifying the specific mechanisms of apomixis, and determining the frequency of apomixis versus sexual reproduction in facultative apomicts.
Q: What role does epigenetics play in apomictic reproduction?
A:
Epigenetics plays a crucial role in apomictic reproduction by regulating gene expression without changing the DNA sequence. Epigenetic mechanisms, such as DNA methylation and histone modifications, can control the switch between sexual and apomictic reproduction in some plant species.

Characteristics Of Apomixis

Apomixis is a special type of asexual reproduction in plants where seeds are formed without fertilisation. This process has some unique features that make it useful for farming and crop improvement, as given below:

  • Asexual Reproduction: Apomixis allows for the production of seeds without the involvement of gametes or fertilization.

  • Genetic Uniformity: Offspring produced through apomixis are genetically identical to the maternal plant.

  • Bypassing stages of meiosis: In some forms of apomixis, the embryo develops from a cell that has not undergone meiosis, maintaining the diploid chromosome number.

  • Potential for Crop Improvement: Apomixis has potential applications in agriculture for the production of hybrid crops and the preservation of desirable traits.

Commonly Asked Questions

Q: How does apomixis affect genetic diversity in plant populations?
A:
Apomixis reduces genetic diversity in plant populations because it produces offspring that are genetically identical to the parent plant. This can limit a species' ability to adapt to changing environments over time.
Q: Why is apomixis considered a form of asexual reproduction?
A:
Apomixis is considered asexual reproduction because it produces offspring without the fusion of male and female gametes. The resulting seeds contain embryos that are genetically identical to the mother plant, bypassing the genetic recombination that occurs in sexual reproduction.
Q: What are some examples of plants that commonly exhibit apomixis?
A:
Some common examples of plants that exhibit apomixis include dandelions, some citrus fruits, and certain grasses like Kentucky bluegrass. These plants can produce seeds without fertilization, allowing them to reproduce even in the absence of pollinators or suitable mates.
Q: What are the potential advantages of apomixis in crop breeding?
A:
Apomixis in crop breeding can allow for the preservation of desirable traits across generations without genetic segregation. This can lead to faster development of new varieties, reduced breeding costs, and the ability to maintain hybrid vigor in subsequent generations.
Q: Can apomixis and sexual reproduction occur in the same plant species?
A:
Yes, some plant species can exhibit both apomixis and sexual reproduction, a phenomenon known as facultative apomixis. This allows plants to benefit from the genetic consistency of apomixis while maintaining the potential for genetic variation through sexual reproduction.

What Is Polyembryony?

Polyembryony is the development of two or more embryos within a single seed or ovule. This process can occur through various mechanisms, including the cell division of the zygote, the development of embryos from nucellar tissue, or the formation of adventitious embryos from other parts of the ovule.

Commonly Asked Questions

Q: How does polyembryony affect seed germination rates?
A:
Polyembryony can increase overall germination rates by producing multiple viable embryos per seed. However, competition among embryos within a seed may result in varying germination times and seedling vigor.
Q: How does polyembryony affect genetic diversity within a single seed?
A:
Polyembryony can result in both increased and decreased genetic diversity within a single seed. When embryos originate from different cells or tissues, they may have distinct genetic compositions. However, if all embryos develop from the same cell lineage, they will be genetically identical.
Q: How does polyembryony affect the concept of genetic identity in clonal plant populations?
A:
Polyembryony complicates the concept of genetic identity in clonal plant populations because it can produce both genetically identical and genetically distinct offspring from the same seed. This can lead to increased genetic diversity within what might otherwise be considered a uniform clonal population.
Q: What are some ecological implications of polyembryony in plant populations?
A:
Polyembryony can increase the reproductive output of individual plants, potentially leading to higher population densities. It can also affect plant-animal interactions, as seeds with multiple embryos may be more attractive to seed predators but also increase the chances of successful dispersal.
Q: How does polyembryony influence plant-pollinator interactions?
A:
Polyembryony generally has little direct effect on plant-pollinator interactions, as it occurs after pollination. However, in facultative apomicts, the balance between sexual and apomictic reproduction may influence the plant's reliance on pollinators and, consequently, its attractiveness to them.

Characteristics Of Polyembryony

Polyembryony is a process where more than one embryo forms in a single seed.This process has some unique features that make it useful for farming and crop improvement, as given below:

  1. Multiple Embryos: A single seed or ovule produces two or more embryos, resulting in the formation of genetically distinct individuals.

  2. Genetic Variation: Polyembryony can lead to genetic variation among the resulting embryos, depending on the origin of the additional embryos.

  3. Asexual Reproduction: In some cases, polyembryony can be considered a form of asexual reproduction, as it allows for the production of genetically identical offspring without the involvement of gametes.

  4. Importance in Agriculture: Polyembryony has applications in agriculture, particularly in the production of clonal planting materials and the development of new cultivars.

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Commonly Asked Questions

Q: How does polyembryony contribute to increased survival rates in some plant species?
A:
Polyembryony can increase survival rates by producing multiple seedlings from a single seed, increasing the chances that at least one will survive. This is especially beneficial in challenging environments where seedling mortality rates are high.
Q: How does polyembryony contribute to the formation of chimeras in plants?
A:
Polyembryony can lead to the formation of chimeras when embryos with different genetic compositions develop within the same seed and fuse during growth. This results in a plant with genetically distinct tissues, which can be valuable for studying gene function and creating unique horticultural varieties.
Q: How does polyembryony affect the concept of "identical twins" in plants?
A:
In plants, polyembryony can produce "identical twins" when multiple embryos develop from the same fertilized egg or maternal tissue. However, unlike human identical twins, plant "twins" from polyembryony may not always be genetically identical, depending on their origin within the seed.
Q: How does the process of nucellar embryony relate to polyembryony?
A:
Nucellar embryony is a specific type of polyembryony where additional embryos develop from the nucellus, a maternal tissue surrounding the embryo sac. This process results in multiple embryos within a single seed, some of which are genetically identical to the mother plant.
Q: How does polyembryony affect seed size and nutrient allocation?
A:
Polyembryony can result in smaller individual embryos within a seed, as the available nutrients and space must be shared among multiple developing embryos. This can affect the initial size and vigor of seedlings upon germination.

Key Differences Between Apomixis And Polyembryony

Apomixis and polyembryony are two distinct phenomena in plants that involve the production of multiple embryos without the fusion of gametes. Understanding the differences between apomixis and polyembryony provides insights into the diversity of reproductive strategies in plants and their potential applications in agriculture and horticulture.

Characteristic

Apomixis

Polyembryony

Definition

Asexual production of seeds or embryos without fertilization

Formation of multiple embryos within a single seed or ovule

Mechanism

An embryo develops from a somatic cell or an unreduced female gametophyte

Multiple embryos develop from the zygote, nucellar tissue, or other parts of the ovule

Genetic Uniformity

Offspring are genetically identical to the maternal plant

Can lead to genetic variation among embryos, depending on their origin

Meiosis

In some forms, the embryo develops from a cell that has not undergone meiosis

Does not necessarily involve bypassing meiosis.

Fertilisation

No fertilisation is involved

Fertilisation may or may not be involved, depending on the mechanism

Agricultural Applications

Potential for production of hybrid crops and preservation of desirable traits

Useful for production of clonal planting materials and development of new cultivars

Examples

Observed in some grasses, Allium, Agave, and Poa

Common in citrus and mango fruits

Significance

Ensures reproduction in the absence of pollinators and avoids costs associated with meiosis

Demonstrates the embryogenic potential of various somatic cells

Commonly Asked Questions

Q: What is the main difference between apomixis and polyembryony?
A:
Apomixis is the production of seeds without fertilization, resulting in genetically identical offspring. Polyembryony is the development of multiple embryos from a single fertilized egg, which can result in genetically identical or different offspring.
Q: Can polyembryony occur in both sexual and asexual reproduction?
A:
Yes, polyembryony can occur in both sexual and asexual reproduction. In sexual reproduction, multiple embryos develop from a single fertilized egg, while in asexual reproduction (like apomixis), multiple embryos can develop from unfertilized egg cells or other maternal tissues.
Q: How does polyembryony differ from twins in human reproduction?
A:
Polyembryony in plants can produce multiple embryos from a single fertilized egg or from maternal tissues, resulting in genetically identical or different offspring. In contrast, human twins typically result from either the splitting of a single fertilized egg (identical twins) or the fertilization of two separate eggs (fraternal twins).
Q: How does the energy cost of producing multiple embryos in polyembryony compare to single-embryo seeds?
A:
Producing multiple embryos in polyembryony generally requires more energy and resources from the parent plant compared to single-embryo seeds. This increased energy cost may be offset by the potential benefits of increased reproductive success and survival rates of offspring.
Q: How does apomixis impact plant breeding and genetic modification efforts?
A:
Apomixis can complicate plant breeding efforts by limiting genetic recombination. However, it can also be advantageous in maintaining desirable traits in crop plants. In genetic modification, apomixis could potentially be used to propagate genetically modified plants without the risk of trait segregation.

MCQs in Apomixis And Polyembryony

Question 1: The Following are certain statements regarding apomixis in plants:

P. Apomixis cannot be used to maintain hybrid vigor over many generations in plants.

Q. In sporophytic apomixis maternal genotype is maintained.

R. There is an event of meiosis during gametophytic apomixis, which is also referred to as apomeiosis.

S. In diplospory, meiosis of the megaspore mother cell is aborted, resulting in two unreduced spores, out of which one forms the female gametophyte.

Which one of the following combinations is correct?

  1. P and Q

  2. P and R

  3. Q and R

  4. Q and R

Answer: Q. In sporophytic apomixis maternal genotype is maintained.

S. In diplospory, meiosis of the megaspore mother cell is aborted, resulting in two unreduced spores, out of which one forms the female gametophyte.

Statement P is incorrect. Apomixis, which involves asexual reproduction, cannot maintain hybrid vigour over many generations since it does not involve the recombination and genetic variation that occur through sexual reproduction.

Statement R is incorrect. Meiosis is not a part of gametophytic apomixis, and it is not referred to as apomeiosis. Gametophytic apomixis involves the development of an embryo from an unreduced egg cell or a modified female gametophyte without the need for fertilization.

Therefore, the correct combination is Q and S. In sporophytic apomixis, the maternal genotype is maintained, and in diplospory, meiosis of the megaspore mother cell is aborted, resulting in two unreduced spores, one of which forms the female gametophyte.

Hence, the correct answer is option 4) Q and S.

Question 2: What is common between vegetative reproduction and apomixis.

  1. Both are applicable only to dicot plants.

  2. Both bypass the flowering phase

  3. Both occur throughout the year

  4. Both produce progeny identical to the parent

Answer: Both vegetative reproduction and apomixis produce progeny that are genetically identical to the parent, referred to as clones. These forms of asexual reproduction do not involve the formation of gametes or fertilization and rely on a single parent for reproduction. In vegetative reproduction, new plants arise from vegetative parts like roots, stems, or leaves, while in apomixis, seeds are formed without fertilization, bypassing the typical sexual reproduction process. Both methods ensure the preservation of genetic uniformity across generations.

Hence, the correct answer is option 4) Both produce progeny identical to the parent.

Question 3: Which of the following is true about polyembryony?

  1. It is a type of asexual reproduction in plants.

  2. It results in the formation of genetically identical offspring.

  3. It involves the development of seeds without fertilization.

  4. A single fertilized egg gives rise to multiple embryos in polyembryony.

Answer: Polyembryony is a phenomenon where a single fertilized egg gives rise to multiple embryos in polyembryony. It is a type of reproductive strategy found in some plants, where the fertilized egg divides multiple times to form multiple embryos, resulting in the development of multiple seedlings from a single seed. Hence option D is the correct answer.

Option(A) Polyembryony is a type of sexual reproduction. Hence option A is incorrect.

Option(B) Polyembryony results in the formation of genetically identical offspring but they are distinct from their parents. Hence option B is incorrect.

Option(C) Apomixis involves the development of seeds without fertilization. Hence option C is incorrect.

Hence, the correct option is 4) A single fertilized egg gives rise to multiple embryos in polyembryony.

Frequently Asked Questions (FAQs)

Q: What are some current research frontiers in understanding the molecular mechanisms of apomixis and polyembryony?
A:
Current research frontiers include: 1) identifying genes and regulatory networks controlling apomixis and polyembryony, 2) understanding epigenetic regulation of these processes, 3) investigating the evolutionary origins and maintenance of apomixis, 4) developing methods to induce apomixis in sexual species for crop improvement, and 5) exploring the potential of gene editing technologies to
Q: How does polyembryony affect the study of quantitative genetics in plants?
A:
Polyembryony complicates quantitative genetics studies in plants by producing offspring with varying degrees of genetic relatedness within a single seed. This can affect estimates of heritability and genetic correlations, requiring specialized experimental designs and statistical approaches to accurately assess genetic parameters.
Q: What is the relationship between apomixis and hybridization in plant evolution?
A:
Apomixis and hybridization often interact in plant evolution. Hybridization events can sometimes trigger the development of apomictic reproduction, while apomixis can stabilize hybrid genotypes that might otherwise be unstable or sterile. This interaction has played a significant role in the evolution of many plant lineages.
Q: How does polyembryony affect the concept of "maternal effects" in plant ecology?
A:
Polyembryony complicates the study of maternal effects because multiple embryos within a seed may experience different microenvironments or resource allocations. This can lead to variation in offspring traits that is not solely attributable to maternal genotype or environment, but also to within-seed competition and position effects.
Q: How does apomixis affect plant responses to climate change and environmental stress?
A:
Apomixis can provide short-term advantages in responding to environmental stress by allowing rapid reproduction of adapted genotypes. However, it may limit long-term adaptive potential by reducing genetic diversity. The balance between these effects can influence how apomictic plant populations respond to climate change and other environmental pressures.
Q: What are some potential applications of polyembryony in plant tissue culture and micropropagation?
A:
Polyembryony can be exploited in plant tissue culture to increase propagation rates of valuable plant species. By inducing polyembryony in vitro, it may be possible to produce multiple clonal plants from a single explant, enhancing the efficiency of micropropagation techniques.
Q: How does apomixis influence the evolution of plant mating systems?
A:
Apomixis can influence the evolution of plant mating systems by providing an alternative to sexual reproduction. In some cases, it may lead to the loss of sexual traits or the evolution of facultative sexual systems. The presence of apomixis can also affect the evolution of self-incompatibility mechanisms and floral traits related to pollinator attraction.
Q: What role does polyembryony play in the life cycles of parasitic plants?
A:
In some parasitic plants, polyembryony can increase the chances of successful host attachment by producing multiple seedlings from a single seed. This strategy can be particularly advantageous for parasitic plants that require specific host species or have limited dispersal capabilities.
Q: How does apomixis affect the distribution of genetic variation within and among plant populations?
A:
Apomixis tends to reduce genetic variation within populations by producing genetically identical offspring. However, it can maintain genetic differences among populations by preserving distinct genotypes. This can lead to a pattern of high between-population genetic diversity but low within-population diversity.
Q: What are some similarities and differences between apomixis in plants and parthenogenesis in animals?
A:
Both apomixis and parthenogenesis are forms of asexual reproduction that produce offspring from unfertilized eggs. However, apomixis in plants often involves complex developmental pathways and can occur through various mechanisms, while parthenogenesis in animals typically involves the direct development of an unfertilized egg into an embryo.
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