The term ‘Partheno’ indicates the asexual mode of reproduction. The term ‘Carpy’ is related to the carpel (female structure), therefore it is a process of plant reproduction. Genesis means to evolve or to generate/to form and is used for animals as well for plants. Difference between parthenocarpy and parthenogenesis for NEET examination is very important as many questions arise from this topic.
Parthenocarpy and Parthenogenesis differences can be made out of the following explanation.
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:
In this process, an embryo develops from haploid eggs and the embryo is haploid. Examples include Datura, Solanum nigrum, and Oenothera.
In this process, an embryo develops from a diploid egg, and the formed embryo is diploid as in Aposporous plants. An example of this includes Hieracium Ranunculus.
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The term Parthenocarpy was introduced by Noll in the year 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 grapes varieties and cucumbers have resulted from mutations in the bud.
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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.
1. What is Amphimixis?
It is a kind of sexual or true reproduction in which both processes - meiosis, and fertilization occur. In meiosis, the chromosome number is reduced to half and in fertilization, the chromosome number is restored (2n).
2. Explain the Terms Apospory and Apogamy.
Apospory is the formation of gametophyte directly from sporophyte i.e. the nucellus or integument without meiosis. The aposporous gametophyte will be in diploid (2n) form. Apogamy is the formation of sporophyte directly from the gametophyte except for egg, without fertilization and here, the sporophyte is haploid. An example of apogamy is Orchis maculata.
3. Explain Polyembryony.
Polyembryony was first discovered by A.V. Leeuwenhoek in the year 1719 in Orange plant and it is commonly seen in citrus plants. It is the occurrence of more than one embryo in the ovule and is common in Gymnosperm since they have many archegonia and may be fertilized and produce more than one embryo. On the other hand, polyembryony in angiosperms is rarely found and it is of two types namely, true polyembryony and false polyembryony. The former condition is extra embryos development within the embryo sac and the latter means extra embryos development outside the embryo sac in nucellus or integument. Suspensor polyembryony and adventive polyembryony are the two types of polyembryony found based on the development process. The application of Polyembryony is significant in agriculture and horticulture as these are genetically uniform and are disease-free.