Polyembryony

Edited By Irshad Anwar | Updated on Jul 02, 2025 07:09 PM IST

Polyembryony is the process in which many embryos develop from a single fertilised egg or ovule. This phenomenon naturally occurs in plants such as citrus, onion, and mango. They can arise from the zygote or from nucellar or integumentary cells. It can be a result of the cleavage of the zygote or the development of embryos from accessory parts.

This Story also Contains

What is Polyembryony?
Characteristics of Polyembryony
Types of Polyembryony
Importance of Polyembryony
Problems and Limitations of Polyembryony
MCQs on Polyembryony
Recommended video on Polyembryony

Polyembryony

The process also ensures a survival advantage by forming multiple embryos and seedlings from a single fertilised ovule. This is important in agriculture and horticulture by producing genetically identical plants, which improves propagation efficiency. Polyembryony is an important topic in biology subject.

What is Polyembryony?

An exciting phenomenon in plants occurs in which a single seed or ovule gives rise to several embryos. This process has great implications for reproduction in plants, agriculture, and plant development studies. Polyembryony helps to understand the plasticity and adaptability of a species of plant.

Polyembryony is the development of two or more embryos in a single seed or ovule. The process can be induced artificially in vitro culture, but it also occurs naturally in some plant species. More than one embryo develops from a single seed or ovule, forming genetically different individuals.

Characteristics of Polyembryony

Polyembryony involves the development of multiple embryos within a single seed. These embryos may arise from the same zygote or different maternal tissues like the nucellus. Depending on their origin, the polyembryony would lead to genetic variation among the resultant embryos.

Asexual Reproduction: In a way, polyembryony can be seen as falling under the category of asexual reproduction because this process makes it possible for an organism to produce offspring that are genetically identical without using gametes.

Importance in Agriculture: There are many uses of polyembryony in agriculture, especially in clonal planting material production and cultivar development.

Types of Polyembryony

It is mainly classified into zygotic, nucellar, and adventitious polyembryony. Polyembryony can result through different mechanisms, leading to the formation of multiple embryos within a single seed or ovule:

Zygotic Polyembryony

In zygotic polyembryony, the division of the zygote leads to the formation of two or more embryos that result in genetically identical individuals. This kind of polyembryony is frequent in citrus fruits and in some other plant species.

Nucellar Polyembryony

Nucellar polyembryony consists of the development of embryos from the nucellar tissue surrounding the embryo sac. These embryos are genetically identical to the maternal plant since they originate from somatic cells. Nucellar polyembryony is found in numerous plants of citrus fruits, mango, and a few other tropical and subtropical plants.

Adventitious Polyembryony

Adventitious embryony occurs when additional embryos develop from the remaining parts of the ovule, such as the integuments or the suspensor. These embryos may or may not be genetically identical to the primary embryo or each other. Examples of plants with this type of polyembryony are some orchids and ferns.

Importance of Polyembryony

One of the most important advantages of this phenomenon is that polyembryony enables the generation of offspring with similar genetic material. This can, therefore, be utilised in crops for the propagation of identical genomes carrying desirable features.

Genetic Diversity: Still, on occasions, polyembryony may lead to variations between the formed embryos, hence offering the advantages of adaptation to plant species.

Embryological Studies: Polyembryony offers scope for the studies of plant embryology and the mechanisms of development of embryos.

Crop Improvement: The knowledge of polyembryony can be utilised to create new crop forms with such deliberate characteristics as high yield or disease resistance.

Problems and Limitations of Polyembryony

Polyembryony may restrict selective breeding, complicate hybrid seed production, and reduce genetic diversity due to uniformity in offspring. The various limitations of polyembryony is discussed below-

Unequal Development: In some cases, the several embryos included in a seed or ovule may not be equally developed, and consequently may be of different sizes and very unequal in vigour.

Low Seed Viability: This polyembryony may sometimes depress the overall viability of seeds because the seed's resources are divided among the many embryos.

Difficulty of Identification: Genetically different embryos are hard to distinguish from clonal ones, especially in the early stages of development.

MCQs on Polyembryony

Q1. In many citrus fruits, poly-embryonic seed formation takes place where one or two nucellar cells start growing as embryos along with the zygotic embryo. As a result, seed germinates to give rise to as many as two or three plantlets. If one wants to grow the plant with the same characteristics as the fruit from which the seed is obtained, which of the plantlets can be used?

Option 1: The one from the zygotic embryo is the best choice as it has hybrid vigour.

Option 2: The nucellus embryo plantlet is a clone of the mother plant.

Option 3: As there will be competition for survival among the three plantlets, the most healthy and largest in size is the best choice.

Option 4: Any of the three as all will have the same phenotypes.

Correct answer: 2) The nucellus embryo plantlet is a clone of the mother plant.

Explanation:

In the case of poly-embryonic seed formation in citrus fruits, where multiple embryos develop within a single seed, the nucellus embryo plantlet can be used to grow a plant with the same characteristics as the mother plant.

The nucellus embryo is derived from the maternal tissue, specifically the nucellus, rather than the fertilization process. Therefore, it is genetically identical or very similar to the mother plant, making it a clone. By using the nucellus embryo plantlet, you can ensure that the resulting plant will have the same characteristics as the fruit from which the seed was obtained.

In contrast, the zygotic embryo is the result of fertilization and contains genetic material from both the male and female parents. It may not have the same characteristics as the mother plant, as genetic variation can occur due to genetic recombination during fertilization.

Therefore, if you want to grow a plant with the same characteristics as the fruit from which the seed is obtained in the case of poly-embryonic citrus fruits, it is preferable to use the nucellus embryo plantlet.

Hence, the correct answer is option 2. The nucellus embryo plantlet is a clone of the mother plant.

Q2. Nucellar polyembryony is reported in species of

Option 1: Citrus

Option 2: Gossypium

Option 3: Triticum

Option 4: Brassica

Correct answer: 1) Citrus

Explanation:

Polyembryony refers to the presence of more than one embryo within a single seed. In plants like Citrus and mango, certain nucellar cells surrounding the embryo sac undergo division and develop into additional embryos, alongside the zygotic embryo. This phenomenon, known as nucellar polyembryony, results in ovules containing multiple embryos, a characteristic feature of these species. Polyembryony has practical significance in horticulture as it often produces genetically identical seedlings from nucellar embryos.

Hence, the correct answer is option 1) Citrus

Q3. Which of the following is true about polyembryony?

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

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

Option 3: It involves the development of seeds without fertilisation.

Option 4: A single fertilised egg gives rise to multiple embryos in polyembryony.

Correct answer: 4) A single fertilised egg gives rise to multiple embryos in polyembryony.

Explanation:

Polyembryony is a phenomenon where a single fertilised egg gives rise to multiple embryos in polyembryony. It is a type of reproductive strategy found in some plants, where the fertilised egg divides multiple times to form multiple embryos, resulting in the development of multiple seedlings from a single seed.

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

Recommended video on Polyembryony

Frequently Asked Questions (FAQs)

1. What is polyembryony?

Polyembryony refers to the development of two or more embryos inside a single seed or ovule.

2. What are the types of polyembryony?

There are essentially zygotic polyembryony, nucellar polyembryony, and adventitious polyembryony as the main types of polyembryony.

3. What are some examples of plants that exhibit this?

Examples include citrus fruits, mango, orchids, and ferns.

4. How then is polyembryony contributing to genetic variation?

Depending on the source of the additional embryos, polyembryony can result in the production of genetically different embryos.

5. What are some potential applications of polyembryony in agriculture?

Applications of polyembryony are in clonal planting material production and the development of new cultivars with desirable characteristics.

6. How does polyembryony differ from normal embryo development?

In normal embryo development, a single zygote forms from the fusion of one egg cell and one sperm cell, resulting in one embryo per seed. In polyembryony, multiple embryos develop, either from the same zygote or from different cellular origins within the ovule.

7. How can polyembryony be detected in seeds?

Polyembryony can be detected through various methods, including: 1) Germination tests, where multiple seedlings emerge from a single seed, 2) Microscopic examination of seed sections to observe multiple embryos, and 3) Genetic analysis to determine the origin and relatedness of the embryos.

8. How does polyembryony affect seed size and nutrient content?

Polyembryonic seeds may be larger than normal seeds to accommodate multiple embryos. However, the nutrient content per embryo may be reduced as the available resources are shared among multiple developing embryos, potentially affecting their initial growth and survival rates.

9. What is the role of endosperm in polyembryonic seeds?

In polyembryonic seeds, the endosperm plays a crucial role in nourishing multiple embryos. It may need to provide nutrients to embryos of different genetic origins and at potentially different developmental stages, which can affect the allocation of resources and the eventual success of each embryo.

10. How does polyembryony impact seed dispersal strategies?

Polyembryony can influence seed dispersal strategies by affecting seed size, weight, and the number of potential seedlings per dispersal unit. This may alter the plant's ability to colonize new areas or compete for resources, as multiple seedlings may emerge in close proximity from a single seed.

11. What is polyembryony in flowering plants?

Polyembryony is the phenomenon where multiple embryos develop from a single fertilized ovule in flowering plants. This results in the formation of more than one seedling from a single seed, which is contrary to the typical development of a single embryo per seed.

12. What are some examples of plants that commonly exhibit polyembryony?

Common examples of plants exhibiting polyembryony include: 1) Citrus species (e.g., oranges, lemons), 2) Mango (Mangifera indica), 3) Eucalyptus species, 4) Some orchids, 5) Onion (Allium cepa), and 6) Groundsel tree (Baccharis halimifolia).

13. How does polyembryony affect the concept of seed viability?

Polyembryony complicates the concept of seed viability because a single seed may contain multiple embryos with different viability levels. This can lead to situations where some embryos within a seed are viable while others are not, affecting germination rates and seedling establishment.

14. What is the significance of polyembryony in plant evolution?

Polyembryony has evolutionary significance as it can serve as a reproductive strategy that balances between sexual and asexual reproduction. It allows plants to produce both genetically diverse and clonal offspring, potentially increasing adaptability to changing environments while maintaining successful genotypes.

15. How does polyembryony affect seed dormancy and germination timing?

Polyembryonic seeds may exhibit complex dormancy and germination patterns due to the presence of multiple embryos. Different embryos within the same seed may have varying dormancy requirements or germination timings, potentially leading to staggered emergence of seedlings.

16. Can polyembryony occur naturally in plants?

Yes, polyembryony can occur naturally in some plant species. It is more common in certain families like Rutaceae (citrus fruits), Myrtaceae (eucalyptus), and Orchidaceae (orchids). However, it can also be induced artificially in some plants for research or agricultural purposes.

17. What is the evolutionary significance of polyembryony?

Polyembryony can provide evolutionary advantages by increasing reproductive success. It allows plants to produce genetically identical offspring (in case of nucellar embryony) or genetically diverse offspring (in case of multiple fertilization events), potentially improving survival chances in varying environmental conditions.

18. How does polyembryony affect seed germination rates?

Polyembryony can increase seed germination rates by producing multiple viable embryos within a single seed. This improves the chances of at least one embryo successfully germinating and establishing as a seedling, potentially enhancing the plant's reproductive success.

19. How does nucellar embryony contribute to genetic uniformity?

Nucellar embryony produces embryos from the maternal nucellar tissue, which is genetically identical to the mother plant. This results in clonal offspring, maintaining genetic uniformity and preserving desirable traits in subsequent generations without genetic recombination.

20. How does polyembryony affect plant breeding and genetic improvement programs?

Polyembryony can complicate plant breeding programs by producing offspring that are genetically identical to the mother plant, making it difficult to introduce new traits. However, it can also be advantageous in maintaining and propagating desirable traits in clonal populations for certain crops.

21. How does polyembryony in citrus fruits impact the citrus industry?

Polyembryony in citrus fruits allows for the production of genetically uniform rootstocks, which is beneficial for maintaining consistent fruit quality and disease resistance. However, it can make breeding new varieties more challenging, as the nucellar embryos often outcompete the zygotic embryos.

22. What are some common misconceptions about polyembryony in plants?

Common misconceptions include: 1) Assuming all embryos in polyembryonic seeds are genetically identical, 2) Believing polyembryony always results in multiple seedlings, 3) Thinking polyembryony is rare in nature, and 4) Assuming all embryos in a polyembryonic seed have equal chances of survival.

23. How does the environment influence the occurrence of polyembryony?

Environmental factors such as temperature, light, and nutrient availability can influence the occurrence and frequency of polyembryony in some plant species. Stress conditions may sometimes trigger polyembryony as a survival strategy, while optimal conditions may favor normal embryo development.

24. What are the agricultural implications of polyembryony?

In agriculture, polyembryony can be both beneficial and challenging. It can be useful for propagating genetically identical plants with desirable traits (e.g., in citrus cultivation). However, it can also complicate breeding programs and seed production when genetic uniformity is not desired.

25. How does polyembryony affect genetic diversity in plant populations?

Polyembryony can have varying effects on genetic diversity. When it results from nucellar or integumentary embryony, it reduces genetic diversity by producing clonal offspring. However, when multiple embryos arise from different fertilization events, it can increase genetic diversity within a single seed.

26. What are the main types of polyembryony in plants?

The main types of polyembryony in plants are: 1) Cleavage polyembryony, where the zygote or proembryo splits to form multiple embryos, 2) Nucellar embryony, where embryos develop from the nucellus tissue, and 3) Integumentary embryony, where embryos form from the integument cells of the ovule.

27. What role does apomixis play in polyembryony?

Apomixis is a form of asexual reproduction in plants where seeds are produced without fertilization. It can lead to polyembryony when multiple embryos develop from unfertilized egg cells or other maternal tissues, resulting in genetically identical offspring.

28. What is the difference between simple and compound polyembryony?

Simple polyembryony refers to the development of multiple embryos from a single source, such as the division of a zygote. Compound polyembryony involves the formation of embryos from different sources within the same seed, such as from the zygote, nucellus, and integuments.

29. What is adventive embryony, and how does it relate to polyembryony?

Adventive embryony is a type of polyembryony where embryos develop from somatic cells of the ovule, such as the nucellus or integuments, rather than from the fertilized egg cell. This process results in embryos that are genetically identical to the mother plant.

30. What is the relationship between polyembryony and apomixis?

Polyembryony and apomixis are related but distinct phenomena. Apomixis is the production of seeds without fertilization, while polyembryony is the development of multiple embryos in a single seed. Some forms of apomixis can lead to polyembryony, but not all cases of polyembryony involve apomixis.

31. What is the relationship between polyembryony and asexual reproduction in plants?

Polyembryony, particularly forms like nucellar embryony, represents a bridge between sexual and asexual reproduction in plants. While it occurs within the context of seed production (typically associated with sexual reproduction), it can result in clonal offspring, a characteristic of asexual reproduction.

32. How does polyembryony impact the concept of maternal effects in plant genetics?

Polyembryony, especially nucellar embryony, can exaggerate maternal effects in plant genetics. Non-zygotic embryos are genetically identical to the mother plant, potentially masking paternal genetic contributions and complicating studies of genetic inheritance and environmental influences on offspring traits.

33. What role does polyembryony play in the evolution of plant mating systems?

Polyembryony can influence the evolution of plant mating systems by providing a mechanism for reproductive assurance. It allows plants to produce both genetically diverse offspring (through zygotic embryos) and clonal offspring (through non-zygotic embryos), potentially balancing the benefits of outcrossing with the stability of selfing.

34. How does polyembryony affect the concept of seed heteromorphism?

Polyembryony adds a layer of complexity to seed heteromorphism – the production of different types of seeds by a single plant. In polyembryonic species, seeds may not only differ in external characteristics but also in their internal composition of embryo types, affecting germination behavior and seedling establishment.

35. How does polyembryony influence the evolution of seed size in plants?

Polyembryony can influence seed size evolution by creating a trade-off between the number of embryos per seed and the resources available for each embryo. This can lead to selection pressures favoring either larger seeds to support multiple embryos or mechanisms to regulate embryo number based on available resources.

36. What are the challenges in studying polyembryony?

Challenges in studying polyembryony include: 1) Difficulty in identifying polyembryonic seeds without germination or dissection, 2) Variability in the frequency and type of polyembryony within species, 3) Complexity in determining the genetic origins of multiple embryos, and 4) Interactions between environmental and genetic factors influencing polyembryony.

37. What are the cellular mechanisms involved in the formation of multiple embryos?

The cellular mechanisms involved in polyembryony can include: 1) Cleavage of the zygote or proembryo, 2) Dedifferentiation and embryogenic development of nucellar or integumentary cells, 3) Formation of multiple egg cells within a single embryo sac, or 4) Development of embryos from synergid cells or antipodal cells.

38. How does polyembryony affect the concept of hybrid vigor in plants?

Polyembryony can complicate the expression of hybrid vigor (heterosis) in plants. While zygotic embryos resulting from cross-pollination may exhibit hybrid vigor, nucellar embryos in the same seed will be genetically identical to the mother plant and may not show the same enhanced traits.

39. What role do plant hormones play in the development of polyembryony?

Plant hormones, particularly auxins and cytokinins, play crucial roles in regulating polyembryony. They can influence the initiation of embryo development from somatic tissues, control the division and differentiation of embryonic cells, and affect the growth and survival of multiple embryos within a seed.

40. How does polyembryony impact the calculation of seed germination percentages in laboratory tests?

Polyembryony can complicate seed germination tests because a single seed may produce multiple seedlings. This can lead to germination percentages exceeding 100% if calculated based on the number of emerged seedlings rather than the number of seeds that produced at least one seedling.

41. What is the relationship between polyembryony and somatic embryogenesis?

Polyembryony and somatic embryogenesis are related concepts. Somatic embryogenesis, the formation of embryos from somatic cells, can occur naturally in some forms of polyembryony (e.g., nucellar embryony). Understanding polyembryony has contributed to the development of artificial somatic embryogenesis techniques for plant propagation.

42. How does polyembryony affect seed storage and longevity?

Polyembryonic seeds may have different storage characteristics compared to single-embryo seeds. The presence of multiple embryos can affect moisture content, metabolic activity, and susceptibility to deterioration during storage, potentially impacting seed longevity and storage protocols.

43. What are the implications of polyembryony for plant conservation efforts?

Polyembryony can have both positive and negative implications for plant conservation. It can help preserve genetic material through clonal reproduction, but may also reduce genetic diversity in populations. Understanding polyembryony is crucial for developing effective conservation strategies for species that exhibit this trait.

44. How does polyembryony influence competition among seedlings?

Polyembryony can lead to intense competition among seedlings emerging from the same seed. This intra-seed competition can affect seedling establishment, with stronger or faster-growing embryos potentially outcompeting their siblings for resources, ultimately influencing which genetic individuals survive.

45. What is the difference between zygotic and non-zygotic embryos in polyembryonic seeds?

In polyembryonic seeds, zygotic embryos result from the fusion of male and female gametes and are genetically distinct from the mother plant. Non-zygotic embryos, such as those from nucellar tissue, are genetically identical to the mother plant. This distinction is important for understanding genetic diversity in offspring.

46. How does polyembryony affect the concept of seed quality in agriculture?

Polyembryony complicates the assessment of seed quality in agriculture. While it can increase the number of potential plants per seed, it also introduces variability in genetic makeup and vigor among embryos. This can affect uniformity in crop establishment and performance, requiring specialized quality control measures.

47. What are the ecological implications of polyembryony in natural plant populations?

Ecologically, polyembryony can influence plant population dynamics by affecting seedling density, genetic diversity, and colonization potential. It can provide a reproductive advantage in certain environments but may also intensify competition among closely related individuals.

48. How does polyembryony relate to the concept of totipotency in plant cells?

Polyembryony, especially in forms like nucellar embryony, demonstrates the totipotency of plant cells – their ability to develop into complete organisms. It showcases how somatic cells in the ovule can dedifferentiate and develop into entire embryos, a principle that is fundamental to many areas of plant biotechnology.

49. What techniques are used to induce artificial polyembryony in plants?

Artificial polyembryony can be induced through techniques such as: 1) In vitro culture of ovules or ovaries, 2) Application of plant growth regulators, 3) Genetic modification to alter embryo development pathways, and 4) Manipulation of environmental conditions during seed development.

50. How does polyembryony affect the interpretation of genetic studies in plants?

Polyembryony can complicate genetic studies by producing offspring with varying degrees of relatedness to the parent plants. This can lead to misinterpretation of inheritance patterns and genetic diversity in populations if the phenomenon is not accounted for in experimental design and data analysis.

51. What are the implications of polyembryony for plant genome sequencing projects?

Polyembryony can complicate plant genome sequencing projects, especially when working with seed-derived material. The presence of multiple embryos with potentially different genetic makeup within a single seed can lead to mixed genomic samples, requiring careful tissue selection and validation of genetic uniformity.

52. What is the significance of polyembryony in understanding plant developmental plasticity?

Polyembryony showcases the developmental plasticity of plant cells and tissues. It demonstrates how plant structures can adapt to produce multiple embryos from various cellular origins, highlighting the flexibility of plant developmental programs in response to genetic and environmental cues.

53. How does polyembryony affect the concept of bet-hedging strategies in plant reproduction?

Polyembryony can serve as a bet-hedging strategy in plant reproduction. By producing multiple embryos with potentially different genetic makeups or developmental timings within a single seed, plants can increase the likelihood of successful offspring establishment under variable or unpredictable environmental conditions.