Difference Between Parthenocarpy and Parthenogenesis

The meaning of the term ‘partheno’ is itself indicative of asexual reproduction. The term ‘carpy’ indicates the female structure (carpals). Lastly, the term ‘genesis’ comes from the Greek word meaning origin. Taken together, these three form the word parthenogenesis, which implies the formation of an offspring from an egg that has not been fertilized. While this is not seen in a lot of beings, especially mammals, this is very commonly observed in the case of bees. 

Parthenogenesis 

The formation of an organism from an unfertilized egg is called parthenogenesis. It can be very well explained with the example of Drone (male bee). Therefore, parthenogenesis can be defined as the formation of an embryo directly from the egg without fertilization. It is of two types:

Haploid Parthenogenesis- In this process, an embryo develops from haploid eggs and the embryo is haploid. Examples include Datura, Solanum nigrum, and Oenothera.

Diploid Parthenogenesis- In this process, an embryo develops from a diploid egg, and the formed embryo is diploid as in Aposporos plants. An example of this includes Hieracium Ranunculus.

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Parthenocarpy

The term Parthenocarpy was introduced by Noll in 1902. It is the phenomenon of fruit formation without fertilization where fruits are seedless. A female reproductive organ of the flower is a carpel that consists of stigma, style, ovary, and ovule. The ovule consists of eggs; normally, after fertilization with the male gamete, the ovary turns into fruit and the ovule turns into a seed. Parthenocarpy is in contrast to this situation since in this condition, the formation of fruits without fertilization takes place. And it is a seedless fruit produced here. It can take place with the injection of plant hormones such as auxin and GA. Examples: seedless grapes and seedless watermelon. Naturally, it occurs in bananas and pineapples.

Genetically, parthenocarpy occurs due to mutations or hybridization. Some of the grape varieties and cucumbers have resulted from mutations in the bud.

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Apomixis

One term related to parthenocarpy is apomixis. However, apomixis differs from parthenocarpy; let’s explore how! During apomixis, the ovule turns into a seed without fertilization, and the ovary converts into a fruit. It can take place in two ways; firstly, if the egg is diploid (2n) instead of haploid (n), secondly, if nucellus forms an embryo, i.e. certain cells in the nucellus perform mitosis and enter embryo sacs to from numerous embryos that make ovule into a seed (this condition is also called polyembryony). It can be said that apomixis is a kind of sexual or true reproduction in which both processes, meiosis, and fertilization are absent. Examples of apomixis in plants include Poa and citrus. 

Zygotic or Suspensor Polyembryony: Cleavage of the apical cells of the globular or filamentous polyembryony produced by the zygote results in two or more embryos in a seed. The multiple embryos that arise from pro-embryonal or suspensor cells are diploid. Example: Orchids. Nucellar or Adventive Polyembryony: Here, diploid nucellus or integument cells form the embryos. Examples: Citrus, Opuntia, and Mangifera.

To differentiate between parthenocarpy and parthenogenesis, we have put a tabular chart below to help students understand in a better way.

Differentiation Between Parthenocarpy and Parthenogenesis

We can thus understand from this, that the main points of distinction between the processes of parthenocarpy and parthenogenesis can be that while parthenocarpy is concerned with the formation of fruit from a non-fertilised uvula, parthenogenesis deals with the growth of the non-fertilised egg into a new individual in the case of animals. The fruit that is formed as a result of parthenocarpy does not contain any seed of its own. However, the offspring produced as a result of parthenogenesis cannot have offspring of their own and is almost always haploid. 

Parthenocarpy simply leads to the production of fruit, but in the case of parthenogenesis, a whole new individual can be formed as a result of the process. Parthenogenesis only happens in invertebrates and some bees, and not in any other animals. The offspring that is produced is exactly identical to the female parent since it is asexual reproduction and hence there is no change in the composition of the genetic material. Despite being genetically female, however, this offspring cannot produce offspring of its own. Both male and female gametes can be formed here but they do not fertilize. 

The queen bee in a hive produces male offspring as a result of parthenogenesis when one of her eggs does not fertilize. The offspring mature and become male drones having haploid chromosomes. 

In mammals, parthenogenesis doesn't happen naturally. This is because even if on the off chance that the female egg fertilizes on its own, mammals go through a process called imprinting, which is crucial to forming DNA. Furthermore, mammals are much bigger in size and consequently, they have a much more complex DNA structure, and the offspring that can be produced on only one set of DNA will not survive anyway. 

However, it is possible to artificially create offspring through the process of parthenogenesis in certain mammals, under lab conditions. The offspring produced will not be very viable and certainly won’t survive in uninhabitable conditions. However, it will have an identical genetic makeup as the parent.