Polyembryony in plants

‘Poly’ means many and “embryony” means embryo. This property is not only limited to plants showing more features of polyembryony than animals as this helps them in the process of reproduction. Understanding Polyembryony, its types, occurrences, and significance will be easier if you read and understand this article.

Plants and Polyembryony

It was Antoni van Leeuwenhoek who discovered this phenomenon in orange seeds for the first time. Gymnosperms have such a high frequency of polyembryony that it could be considered a distinguishing characteristic of this group. Women gametophytes develop two or more arches in the majority of gymnosperms that have polyembryony in their reproductive organs. Because each archegonium contains an egg, the presence of multiple archegonium results in the fertilisation of two or more eggs, resulting in the formation of two or more possible embryos in the process.

Multiple embryonic developments in different Gymnosperm groups

Polyembryony in Cycadales:

  1. Simple polyembryony is a condition that occurs infrequently in this category.
  2. It was discovered in Cycas Circinalis for the first time by A.N Rao.

Coniferales:

  1. Simple polyembryony is found in the majority of members of the Coniferales, with the number of embryos ranging from two to numerous.
  2. Taxodiaceae, Cupressaceae, Pinaceae, and Podocarpaceae are just a few of the families that have been identified as having cleavage polyembryony.
  3. In Cupressus, both types of polyembryony are common occurrences.

Taxales:

  1. The female gametophyte of Taxus has many archenemies, which means she has many different kinds of eggs. At the end of the process, however, only one embryo becomes fully developed.
  2. In Taxus, cleavage of the suspensor cell has been observed. They are separated from one another and may contain one or more embryonal units in each of their respective compartments.
  3. Clusters of meristematic cells can be found at the base of the suspensor cells on occasion. These clusters of cells are what make up the rosette embryos.

Gnetales:

  1. Occasionally, cells in the secondary suspensor will become meristematic, which results in a large number of embryos being produced.
  2. The primary suspensor tubes are capable of producing an embryo at the tip of each tube, resulting in a large number of embryos being produced.
  3. The embryonal mass at the tip of the secondary suspensor may continue to grow and give birth to more embryos in the future.
  4. Occasionally, cells in the secondary suspensor will become meristematic, which results in a large number of embryos being produced.5. Alternatively, two or more cell groups may be formed within the main suspensor tube instead of a single group, resulting in an increased number of embryos at the top.
  5. Gnetum, Melinjo, Ephedrales, Oblongum, and other names are examples of genitive forms.

Angiosperms

Angiosperms exhibit a one-of-a-kind phenomenon known as double fertilisation.

  1. Cleavage of the Zygote:

A single fertilised egg produces a large number of embryos in this type of fertilisation. Plants such as Nicotiana, Orchids, Exocarpos, Nymphaea, and others are examples of this.

  1. Fertilisation of Synergids:

A large number of embryos are formed or produced as a result of the fertilisation of eggs with synergids in combination. For example, Anemone, Sagittaria, Aristolochia, and so on.

  1. Fertilisation of Antipodal Plants:

The formation or production of a large number of embryos occurs as a result of the fertilisation of eggs along with antipodal cells. For example, Paspalum, Ulmus, and so on.

  1. The formation of numerous embryos from structures outside the embryo-sac (adventive polyembryony), such as the nucellus and integuments of plants such as citrus, mango, and Opuntia.

Classification of Polyembryony

  1. True Polyembryony

True polyembryony is defined as the formation of more than one embryo in the same embryo-sac of the ovule during a pregnancy. Additionally, antipodal cells or synergids are responsible for producing the additional embryo(s), which are created either through the cleavage of an egg or by the antipodal cells or synergids.

  1. False Polyembryony 

False polyembryony is defined as the formation of more than one embryo in different embryo sacs within the ovule, rather than in the same embryo sac.

What Is the Importance of Polyembryony?

  1. This phenomenon is extremely important in the fields of plant breeding and horticulture. Citrus nucellar seedlings are superior clones of orchard stock when compared to cuttings in the field of horticulture.
  2. Alternatively, nucellar embryos are intended to be disease-free, whereas nucellar seedlings are intended to restore the vigour that has been lost as a result of continuous cutting propagation.
  3. The adventive polyembryony found in citrus and mango plants is extremely beneficial to the growth of the plants.
  4. Using adventive embryos to produce genetically homogeneous fruit tree seedlings is also critical for producing genetically homogeneous fruit trees.
  5. The haploids can be used to produce homozygous diploids, which are extremely valuable in many situations.

Conclusion

It is defined as the formation of multiple embryos in a single egg or seed, or by the complete cleavage of an unfertilized egg, in the course of a fertilised egg’s development. We gained a better understanding of the different types of polyembryony in plants as a result of this article. Polyembryony was once considered a negative trait, but it is now recognised as a desirable trait in citrus fruits, roses, mangoes, apples, Jamuns, almonds, and other similar fruits to produce high-quality products of genuine value. It contributes to the preservation of the resemblance between parents and children. It is possible to keep the vitality of nucellar seedlings while also keeping them disease-free.

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