Parthenocarpy

What is Parthenocarpy?

Parthenocarpy could be defined as a process by which fruits are produced without the process of fertilisation of ovules. A parthenocarpic fruit is devoid of embryo and endosperm and therefore does not have any seeds. That is why they are also known as seedless or virgin fruits.

The process was first introduced in 1902. During the cultivation of plants, Parthenocarpy is introduced alongside a range of plant hormones which parthenocarpic fruits include Gibberellic acid. This results in the maturation of ovary without fertilisation, leading to the products of big and pulpy fruits.

Parthenocarpic fruit examples include Banana, pineapple, cucumber, watermelon etc.

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What are the Types of Parthenocarpy?

Parthenocarpy can be classified into three different categories

  1. Vegetative parthenocarpy

  2. Stimulative parthenocarpy 

  3. Stenospermocarpy

Vegetative Parthenocarpy

This type of Parthenocarpy takes place without pollination which results in no seed production within seeds. It can be seen in pears and figs to name a few.

Stimulative Parthenocarpy

This also takes place without the pollination, however, there is the usage of an external stimulator. This can be the ovipositor of a wasp inserted into the ovary of a flower or application of plant growth regulators into unisexual flowers which are observed inside the syconium. (Syconium is a flask-shaped structure line with unisexual flowers.)

Stenospermocary

This is a unique type of parthenocarpy where fertilisation does take place and the seed begins to develop but it eventually aborts. There’s a seed trace which can be observed within the fruit and it can be outlined where seed development was terminated. This type of Parthenocarpy can be seen in seedless grapes and watermelons. 

Breeders of seedless fruits take advantage of underdeveloped seeds before they are aborted. These see partially developed seeds are removed from the fruit and grown into plants using tissue culture techniques. The seedless trait is passed on to both parents which assist in the production of high yield of seedless offsprings.

Explanation of Parthenocarpy with an Example

The following summary explains how parthenocarpy takes place in Stenospermocarpy using seedless watermelons as an example.

Stenospermocarpy takes place due to several reasons. One of them is having three sets of chromosomes. Whilst most organisms have even numbers of chromosomes so the resulting pollen and egg cells also receive the same, seedless watermelons of having three sets of chromosomes in each cell. These cells are known as triploids and when they form pollen and egg cells, they do not receive an equal set of chromosomes. The information needed to produce a viable cell is not available due to this reason and therefore resulting in abortion of seed development.

Triploid organisms are naturally developed or they can produce by crossing a diploid cell with a  tetraploid cell which results in a triploid cell.

Triploid pollens are poorly formed and since they cannot germinate diploid varieties are interplanted to induce fruit production with underdeveloped seeds. In seedless watermelons, the traces of seeds are visibly seen.

It should also be mentioned that stenospermocarpy seedlessness in fruits is due to a naturally occurring point mutation in the part of the grape chromosome which is responsible for seed development.

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Diagrammatic Representation of Parthenocarpy

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What are the advantages and disadvantages of parthenocarpy?

Parthenocarpy has its advantages and disadvantages. Both are briefly explained below.

Advantages:

It is very much popular amongst horticulturists. Seedless fruits are more preferred for the production of jams, sauces and fruit drinks. This process also increases the fleshy part of fruits. 

The process also allows a grower to keep pests and insects away from crops without using pesticides. As there is no need for a pollinating insect, plants can be covered to prevent harmful insects from attacking the crops.

Disadvantages: 

Parthenocarpy can also be chemically induced and in such cases, it is harmful to the plant and fruit yields. For example, early application of phytohormones such as auxins before the flowering period or the opening of the flower bud (also known as anthesis) can damage the flowers which lead to abortion to abortion of seed and fruit drop. 

FAQ (Frequently Asked Questions)

1. What is the definition of parthenocarpy and what is a parthenocarpic fruit?

Parthenocarpy can be defined as a process of developing seedless fruits. It can occur naturally or can be artificially induced. In this process, the ovules are not fertilised leading to no formation of seed/s within the fruit. 

A parthenocarpic fruit is produced using parthenocarpy. This type of fruit does not have embryo or endosperm. They are seedless and also known as virgin fruits. 

Examples: Seedless grapes, seedless bananas etc.

2. What is artificial parthenocarpy?

When plant hormones such as auxin, cytokinin and gibberellins to stimulate the development of parthenocarpic fruits, the process is known as artificial parthenocarpy. It is also referred to as induced parthenocarpy.

3. What is apomixis and how does it differ from parthenocarpy?

Apomixis can be described as the formation of seed without fertilisation. The formation of seed and fruit starts with pollination and subsequent cell division and fertilisation. However, in this process, meiotic cell division doesn't take place and there is also no fertilisation of the gametes to form a zygote.

If apomixis occurs from the diploid sporophyte is known as Sporophytic apomixis and similarly, if it occurs the haploid gametophyte it is known as gametophytic apomixis.


The differences

Other than the general difference of one is the production of fruit without fertilisation and the other is the production seed without fertilisation, Apomixis produces genetically identical mother cells whilst parthenocarpy produces genetically identical offspring.

Apomixis is seen in angiosperms and gymnosperms whilst parthenocarpy can be seen in all types of plants.

4. How does parthenocarpy affect plant biodiversity?

According to many environmentalists, producing parthenocarpic crops decreases plant biodiversity which in turn reduces a plant species; resistance to disease. Aso transfer of genes from seedless crops to unmodified crops can make them sterile.