Difference Between Somatic And Zygotic Embryogenesis

Edited By Irshad Anwar | Updated on Jul 02, 2025 07:10 PM IST

Embryogenesis is the embryo formation and development in plants, with the starting material that could be a fertilised zygote or somatic cells. The process has stages such as cell division and differentiation, forming plant structures such as roots, shoots, and cotyledons.

There are mainly two types of embryogenesis: zygotic embryogenesis, which occurs naturally from a fertilised egg, and somatic embryogenesis, which is artificially induced from non-reproductive cells in lab conditions. Zygote is a result of sexual reproduction, while somatic embryos are clones of their parent and are required for plant tissue culture and biotechnology. Zygotic and Somatic Embryogenesis are important topics in the field of biology.

This Story also Contains

What is Embryogenesis?
Zygotic Embryogenesis
Somatic Embryogenesis
Differences Between Somatic And Zygotic Embryogenesis
MCQs on Differences Between Somatic And Zygotic Embryogenesis

Difference Between Somatic And Zygotic Embryogenesis

What is Embryogenesis?

Embryogenesis is the process by which an embryo arises from a fertilised egg or zygote. Embryogeny is composed of a well-coordinated series of stages, from cell division to differentiation and organ formation, until a mature embryo is formed. Hence, embryogenesis is very important in the development of multicellular organisms, since it lays the base for the construction of all tissues and organs.

It ensures the proper formation of a plant and animal body and its functioning. In plants, it makes sure that seeds are formed and thus leads to new plants, while in animals, it leads to the development of an entire living organism from a single cell.

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Zygotic Embryogenesis

Zygotic embryogenesis is a natural process. It initiates with the fertilisation of the egg by a sperm, which leads to the formation of a zygote.

Process of Zygotic Embryogenesis

It is the process of embryonic development that takes place following fertilisation.
It is the zygote that forms as a result of fertilisation.
Cell division occurs following zygote formation.
A cell differentiates into specific cells.

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Stages of Zygotic Embryogenesis

Fertilisation: Sperm and Egg are fertilised, which is called a zygote.
Zygote Formation: Single-cell zygote is formed.
Cell Division: Rapid mitosis occurs in the zygote.
Differentiation: Division into specialised cells forming different tissues and organs.

Examples of Zygotic Embryogenesis

In Plants, Zygotic embryogenesis relates to the development of seeds in flowering plants.
In Animals, embryonic development in mammals.
It provides genetic variability as it occurs sexually.

Applications of Zygotic Embryogenesis

Zygotic embryogenesis plays a significant role in natural processes and ecological balance.

It guarantees diversity in the genome due to the sexual reproduction of species.
Provides genetic variability within a population.
Promotes evolutionary processes and adaptation to habitats.

Somatic Embryogenesis

Somatic embryogenesis is an artificial embryo development from somatic cells, which are non-reproductive cells.

Process of Somatic Embryogenesis

Embryogenesis occurs due to the induction of somatic cells to form a zygote.
It can also be done in vitro, i.e., in a laboratory.

Stages of Somatic Embryogenesis

Initiation: Somatic cells are cultured
Induction: Cells perform embryogenesis
Proliferation: The Embryo starts to proliferate and differentiate.
Maturation: The embryo develops and matures
Germination: The mature embryo leads to the formation of a plant.

Significance Of Somatic Embryogenesis

Important in plant biotechnology and agriculture
Used in cloning and genetic engineering
It is extensively used in tissue culture, particularly in orchid propagation.

Differences Between Somatic And Zygotic Embryogenesis

Zygotic embryogenesis occurs naturally from a fertilised egg cell and leads to genetically diverse offspring, while somatic embryogenesis is an artificial method where embryos develop from somatic (non-reproductive) cells, producing genetically identical plants.

Feature	Zygotic Embryogenesis	Somatic Embryogenesis
Origin	Begins with a zygote.	Begins with somatic (non-reproductive) cells.
Natural vs Artificial	Natural process.	It can be induced artificially.
Genetic Variation	High genetic variation.	Low genetic variation, clones.
Applications	Natural reproduction.	Cloning, genetic engineering, and conservation.

MCQs on Differences Between Somatic And Zygotic Embryogenesis

Q1. Which of the following statements is true?

Statement 1: The growth and development of an embryo from a zygote in flowering plants is known as embryogenesis.

Statement 2: The phases of embryo development are the same in monocot and dicot plants.

Option 1: Statement 1 is correct but Statement 2 is incorrect

Option 2: Statement 2 is correct but Statement 1 is incorrect

Option 3: Both the statements are correct

Option 4: Both the statements are incorrect

Correct Answer: (3) Both the statements are correct

Explanation:

Statement 1: The growth and development of an embryo from a zygote in flowering plants is known as embryogenesis. Embryogenesis is a fundamental process in the life cycle of flowering plants, where a zygote formed through fertilization develops into a mature embryo within a seed. This process involves various stages and cellular changes, leading to the formation of different tissues and organs in the developing embryo.

Statement 2: The phases of embryo development are generally the same in monocot and dicot plants. Although there may be some variations and differences in timing, the overall sequence and major events of embryo development are conserved among flowering plants, regardless of whether they are monocots (e.g., grasses) or dicots (e.g., roses, beans). Both types of plants undergo processes such as the formation of the embryo proper, differentiation of cotyledons, and development of the embryonic root and shoot systems.

Hence, the correct answer is option 3) Both statements are true

Q2. Embryogeny correctly defined as

Option 1: Formation of embryo

Option 2: Development of embryo

Option 3: Also called embryogenesis

Option 4: All of these

Correct Answer: (4) All of these

Explanation:

Embryogeny is the formation and development of an embryo and also known as embryogenesis.

Hence, the correct answer is option (4) All of these

Q3. Select the correct order

Option 1: Zygote --> Globular embryo --> Mature embryo --> Heart shaped embryo

Option 2: Globular embryo --> Mature embryo --> Heart shaped embryo --> Zygote

Option 3: Zygote --> Globular embryo --> Heart shaped embryo --> Mature embryo

Option 4: Zygote --> Heart shaped embryo --> Globular embryo --> Mature embryo

Correct Answer: (3) Zygote --> Globular embryo --> Heart shaped embryo --> Mature embryo

Explanation:

In the process of fertilization in plants, the embryo develops at the micropylar end of the embryo sac, where the zygote is located. The zygote undergoes division only after a certain amount of endosperm is formed. This sequence is an important adaptation that ensures a sufficient supply of nutrients for the developing embryo. The endosperm, which forms after fertilization, acts as a source of stored food, providing energy and nutrients to the growing embryo. This mechanism helps the embryo receive the necessary resources for its growth and development, ensuring the survival of the plant's offspring.

Hence, the correct answer is option (3) Zygote --> Globular embryo --> Heart-shaped embryo --> Mature embryo

Read more:

Pollen-Pistil Interaction & Outbreeding Devices	Artificial Hybridization in Plants - Emasculation and Bagging
Self incompatibility	Post Fertilization - Events and Changes in Flowering Plants
Polyembryony	Parts Of A Seed

Frequently Asked Questions (FAQs)

1. What is somatic embryogenesis?

Somatic embryogenesis is a process in which the somatic or non-reproductive cells develop into embryos.

2. What is zygotic embryogenesis?

It is the process of development that takes place from a fertilized egg, called the zygote, and ends in an embryo.

3. How does somatic embryogenesis differ from zygotic embryogenesis?

There exist differences in their origin, content of genetic variation, and whether they are naturally or artificially inducible.

4. What are some of the applications of somatic embryogenesis in agriculture?

These include plant cloning, genetic engineering, and conservation of endangered plant species.

5. Why is zygotic embryogenesis important?

It is of importance to plants and animals concerning natural reproduction, maintenance of genetic diversity, and evolution.

6. Can somatic embryos develop into full plants?

Yes, somatic embryos can develop into full plants. They have the potential to grow into complete plants with roots, stems, and leaves, just like zygotic embryos. This ability is due to the totipotency of plant cells.

7. Why is somatic embryogenesis important in plant biotechnology?

Somatic embryogenesis is important in plant biotechnology because it allows for rapid clonal propagation of plants, production of transgenic plants, and conservation of rare or endangered species. It's a valuable tool for mass production of genetically identical plants.

8. What are the advantages of somatic embryogenesis over traditional plant propagation methods?

Somatic embryogenesis offers several advantages, including rapid multiplication of plants, production of disease-free plants, year-round production independent of growing seasons, and the ability to produce large numbers of genetically identical plants.

9. Can all plant species undergo somatic embryogenesis?

While many plant species can undergo somatic embryogenesis, not all species have this ability. Some species are more amenable to somatic embryogenesis than others, and the process can be challenging to induce in certain plants.

10. Can somatic embryogenesis occur naturally in plants?

While somatic embryogenesis is primarily induced in laboratory conditions, it can occur naturally in some plant species. For example, some plants can produce embryos from the edges of leaves or in place of seeds, a phenomenon known as apomixis.

11. What are the key stages of somatic embryogenesis?

The key stages of somatic embryogenesis are: induction of embryogenic cells, proliferation of embryogenic cells, formation of pro-embryos, development of globular embryos, and maturation of embryos through heart-shaped, torpedo-shaped, and cotyledonary stages.

12. What triggers somatic embryogenesis in plants?

Somatic embryogenesis is typically triggered by stress conditions or exposure to plant growth regulators, particularly auxins. These factors induce reprogramming of somatic cells to an embryogenic state.

13. What role do plant hormones play in somatic embryogenesis?

Plant hormones, particularly auxins and cytokinins, play crucial roles in somatic embryogenesis. Auxins are often used to induce embryogenic callus formation, while a balance of auxins and cytokinins is important for embryo development and maturation.

14. What is meant by "embryogenic competence" in somatic cells?

Embryogenic competence refers to the ability of somatic cells to respond to embryogenic signals and develop into embryos. Not all somatic cells have this competence, and it can be influenced by factors like cell type, age, and physiological state.

15. How does epigenetics influence somatic embryogenesis?

Epigenetics plays a crucial role in somatic embryogenesis by regulating gene expression without changing the DNA sequence. Epigenetic changes, such as DNA methylation and histone modifications, can affect the ability of somatic cells to become embryogenic and develop into embryos.

16. What is the main difference between somatic and zygotic embryogenesis?

Somatic embryogenesis occurs in vegetative cells of a plant, while zygotic embryogenesis occurs after fertilization of an egg cell. Somatic embryos develop from non-reproductive cells, whereas zygotic embryos develop from a fertilized egg (zygote).

17. How does the origin of somatic and zygotic embryos differ?

Somatic embryos originate from somatic (non-reproductive) cells like leaves, stems, or roots, while zygotic embryos originate from the fertilization of an egg cell by a sperm cell, forming a zygote.

18. How does the developmental process differ between somatic and zygotic embryos?

While both types of embryos go through similar developmental stages, somatic embryos often develop faster and more synchronously than zygotic embryos. Zygotic embryos also undergo a period of dormancy, which is usually absent in somatic embryos.

19. How does the nutritional source differ for somatic and zygotic embryos?

Zygotic embryos receive nutrients from the endosperm of the seed, while somatic embryos obtain nutrients from the culture medium in which they are grown. This difference can affect the development and maturation of the embryos.

20. Are somatic embryos genetically identical to the parent plant?

Yes, somatic embryos are genetically identical to the parent plant because they develop from somatic cells through mitosis. This makes them clones of the parent plant, unlike zygotic embryos which have genetic contributions from both parents.

21. What role does programmed cell death play in somatic and zygotic embryogenesis?

Programmed cell death is important in both types of embryogenesis for proper tissue formation and organ development. In somatic embryogenesis, it may also be involved in the transition of somatic cells to an embryogenic state.

22. How does the concept of totipotency apply to somatic and zygotic embryogenesis?

Totipotency, the ability of a cell to give rise to all cell types in an organism, is fundamental to both processes. In zygotic embryogenesis, it's exhibited by the zygote, while in somatic embryogenesis, differentiated cells regain totipotency.

23. What is the role of auxin gradients in somatic and zygotic embryogenesis?

Auxin gradients are crucial for establishing polarity and patterning in both types of embryogenesis. In somatic embryogenesis, manipulating auxin gradients in culture can influence embryo development and orientation.

24. How do the genes involved in somatic embryogenesis compare to those in zygotic embryogenesis?

Many of the same genes are involved in both processes, particularly those related to embryo patterning and development. However, the timing and regulation of gene expression can differ between somatic and zygotic embryogenesis.

25. What role do reactive oxygen species play in somatic and zygotic embryogenesis?

Reactive oxygen species act as signaling molecules in both types of embryogenesis, influencing cell division and differentiation. However, their levels and effects may differ between somatic and zygotic embryos due to differences in the embryo environment.

26. What is the significance of the suspensor in zygotic embryogenesis, and how does this differ in somatic embryogenesis?

In zygotic embryogenesis, the suspensor connects the embryo to the maternal tissue and aids in nutrient transfer. Somatic embryos typically lack a suspensor, which can affect their development and orientation.

27. How does the presence of endosperm differ between somatic and zygotic embryos?

Zygotic embryos develop alongside endosperm, which provides nutrition during embryo development and early seedling growth. Somatic embryos lack endosperm and must be provided with nutrients artificially in the culture medium.

28. How does the environment affect somatic and zygotic embryogenesis differently?

Zygotic embryogenesis occurs within the protected environment of the ovule, while somatic embryogenesis typically occurs in artificial culture conditions. This means that somatic embryos are more directly influenced by environmental factors like temperature, light, and nutrient availability.

29. How does the ploidy level of somatic embryos compare to zygotic embryos?

Somatic embryos typically have the same ploidy level as the parent plant, which is usually diploid in most flowering plants. Zygotic embryos are also typically diploid, resulting from the fusion of haploid gametes.

30. How does the success rate of somatic embryogenesis compare to zygotic embryogenesis?

The success rate of somatic embryogenesis is generally lower than zygotic embryogenesis. Many somatic embryos fail to develop fully or convert into plants, while zygotic embryos have evolved to have a higher success rate in natural conditions.

31. What are the challenges in achieving successful somatic embryogenesis?

Challenges in somatic embryogenesis include inducing embryogenic competence in recalcitrant species, maintaining genetic stability, preventing somaclonal variation, achieving proper embryo maturation, and successfully converting embryos into plants.

32. What is somaclonal variation and how does it relate to somatic embryogenesis?

Somaclonal variation refers to genetic or phenotypic changes that can occur in plants derived from somatic cells. In somatic embryogenesis, this can lead to plants that differ from the parent, which can be both a challenge and an opportunity for plant breeding.

33. How does the concept of polarity apply to somatic and zygotic embryos?

Both somatic and zygotic embryos establish polarity early in development, determining the future root-shoot axis. However, the cues for establishing polarity may differ, with zygotic embryos influenced by maternal tissues and somatic embryos by culture conditions.

34. What is meant by "embryo rescue" and how does it relate to these two types of embryogenesis?

Embryo rescue is a technique used to save embryos that might otherwise abort. It's typically applied to zygotic embryos from wide crosses but can also be used with somatic embryos that have difficulty maturing in culture.

35. What are the implications of somatic embryogenesis for plant evolution and adaptation?

Somatic embryogenesis provides a mechanism for asexual reproduction and rapid propagation, which can be advantageous for plant survival and adaptation. It also offers opportunities for studying plant developmental plasticity and stress responses.

36. How do the energy requirements differ between somatic and zygotic embryogenesis?

Zygotic embryos rely on stored energy in the seed, while somatic embryos depend on exogenous energy sources in the culture medium. This difference can affect embryo metabolism and development.

37. How does the concept of embryo dormancy apply to somatic and zygotic embryos?

Zygotic embryos typically undergo a period of dormancy before germination, regulated by hormones and environmental cues. Somatic embryos usually lack this dormancy period, which can affect their storage and germination characteristics.

38. What are the ethical implications of somatic embryogenesis in plant biotechnology?

Somatic embryogenesis raises ethical questions related to genetic modification, biodiversity conservation, and the potential for creating large numbers of genetically identical plants. It's important to consider these implications in plant biotechnology applications.

39. How does the maternal influence differ between somatic and zygotic embryogenesis?

Zygotic embryos are strongly influenced by maternal tissues and signals throughout development. Somatic embryos lack this direct maternal influence, which can affect their development and gene expression patterns.

40. What is the significance of embryo size in somatic versus zygotic embryogenesis?

Somatic embryos are often smaller than their zygotic counterparts, which can affect their vigor and survival rate. Understanding and addressing these size differences is important for successful plant regeneration from somatic embryos.

41. How does the concept of embryo competition apply to somatic and zygotic embryogenesis?

In zygotic embryogenesis, multiple embryos may compete for resources within a seed, with usually only one surviving. In somatic embryogenesis, competition occurs between embryos in culture, which can affect embryo quality and development.

42. What is the role of stress in inducing somatic embryogenesis, and how does this compare to zygotic embryogenesis?

Stress often triggers somatic embryogenesis, reprogramming somatic cells to an embryogenic state. In contrast, zygotic embryogenesis is a normal part of the plant life cycle and isn't typically induced by stress.

43. How do the nutritional requirements change during the course of somatic and zygotic embryo development?

Both types of embryos have changing nutritional needs as they develop. In zygotic embryos, these are met by changes in the endosperm, while in somatic embryos, the culture medium must be adjusted to meet these changing needs.

44. What is the significance of embryo-to-plant conversion rates in somatic embryogenesis?

Embryo-to-plant conversion rates are crucial in somatic embryogenesis, as they determine the efficiency of the process. These rates are typically lower than in zygotic embryogenesis and are a key area for improvement in somatic embryogenesis protocols.

45. How does the concept of embryo quality apply differently to somatic and zygotic embryos?

Embryo quality in zygotic embryos is largely determined by natural selection, while in somatic embryogenesis, it's influenced by culture conditions and must be carefully monitored and controlled to ensure viable plant regeneration.

46. How does the concept of embryo synchrony differ between somatic and zygotic embryogenesis?

Somatic embryos often develop more synchronously than zygotic embryos, especially in controlled culture conditions. This synchrony can be advantageous for mass propagation but may not reflect the natural variability seen in zygotic embryo development.

47. What is the significance of cell wall changes during somatic and zygotic embryogenesis?

Cell wall composition and structure change during both types of embryogenesis, influencing cell division, expansion, and differentiation. These changes may occur differently in somatic embryos due to the artificial culture environment.

48. How does the concept of embryo plasticity apply to somatic and zygotic embryogenesis?

Embryo plasticity, or the ability to adapt to environmental changes, is important in both processes. Somatic embryos may exhibit greater plasticity due to their development in artificial conditions, which can be both an advantage and a challenge.

49. What is the role of DNA methylation in somatic and zygotic embryogenesis?

DNA methylation is an important epigenetic mechanism in both processes, regulating gene expression during embryo development. The patterns of DNA methylation may differ between somatic and zygotic embryos, affecting their development and characteristics.

50. How does the concept of embryo maturation differ between somatic and zygotic embryogenesis?

Zygotic embryo maturation involves accumulation of storage compounds and preparation for dormancy. Somatic embryo maturation often requires specific treatments to mimic these processes and prepare embryos for germination or cryopreservation.

51. What is the significance of embryo orientation in somatic and zygotic embryogenesis?

Proper embryo orientation is crucial for normal development in both processes. In zygotic embryos, orientation is influenced by the seed structure, while in somatic embryos, it must be controlled through culture conditions.

52. How does the concept of embryo autonomy apply to somatic and zygotic embryogenesis?

Zygotic embryos gradually become autonomous from maternal tissues during development. Somatic embryos are autonomous from the start, which can affect their development and nutritional requirements.

53. What is the role of non-coding RNAs in somatic and zygotic embryogenesis?

Non-coding RNAs, including microRNAs and long non-coding RNAs, play important regulatory roles in both types of embryogenesis. Their expression patterns and functions may differ between somatic and zygotic embryos.

54. How does the concept of embryo identity apply to somatic and zygotic embryogenesis?

Establishing and maintaining embryo identity is crucial in both processes. In somatic embryogenesis, ensuring proper embryo identity can be challenging and is influenced by culture conditions and the origin of the embryogenic cells.

55. What are the implications of somatic embryogenesis for understanding plant developmental biology?

Somatic embryogenesis provides a valuable model system for studying plant embryo development, allowing researchers to manipulate and observe embryo formation outside of the seed context. This can provide insights into the fundamental processes of plant development and regeneration.