Difference Between Apomixis and Parthenocarpy

Main Difference – Apomixis vs Parthenocarpy

Fruit and the seed are responsible for the propagation of plants. The fruit aids the production, protection, and dispersal of seeds. Usually, the seed and the fruit develop after the pollination and fertilization. Apomixis and parthenocarpy are two mechanisms involved in the production of seeds and fruits in angiosperms, respectively. Apomixis is a type of parthenocarpy. The main difference between apomixis and parthenocarpy is that apomixis is the production of seeds without fertilization whereas parthenocarpy is the production of fruits without seeds. In order to produce a seed, the ovule in the female gametophyte should be fertilized. If not, seed-less fruit bodies are produced. However, parthenocarpy may lead to vegetative reproduction.

Key Areas Covered

1. What is Apomixis
– Definition, Mechanism, Types
2. What is Parthenocarpy
– Definition, Mechanism, Types
3. What are the Similarities Between Apomixis and Parthenocarpy
– Outline of Common Features
4. What is the Difference Between Apomixis and Parthenocarpy
– Comparison of Key Differences

Key Terms: Agamospermous, Apomixis, Asexual Reproduction, Bulbils, Fertilization, Fruit, Parthenocarpy, Plantlets, Seed, Stimulative Parthenocarpy, Vegetative Parthenocarpy

What is Apomixis

Apomixis refers to a type of asexual reproduction that replaces the normal sexual reproduction in plants. It is also known as asexual seed formation. The term, apomixis is currently used synonymously with the term ‘agamospermous‘. The seed is formed by the mother’s tissues of the ovule and therefore, apomixis avoids meiosis as well as fertilization. As angiosperms and gymnosperms are the only seed-producing plants, the apomixis is restricted to those two plant groups. Apomixis utilizes the sexual parts of the plant for vegetative propagation or grafting. The two main mechanisms of apomixis are the replacement of the seed by a plantlet and the replacement of the flower by bulbils. The plantlets are shown in figure 1.

Difference Between Apomixis and Parthenocarpy

Figure 1: Plantlets of Agave angustifolia

Both mechanisms occur through three developmental processes. First, a cell that is capable of developing into an embryo is generated. This prevents prior meiosis (apomeiosis). Then, the embryo develops spontaneously and independently from fertilization (parthenogenesis). Finally, the endosperm develops autonomously or it is derived from fertilization.

What is Parthenocarpy

Parthenocarpy refers to the development of a fruit without prior fertilization. The fruit is known as virgin fruits in parthenocarpy. The ovule is not fertilized by a sperm in these fruits. Thus, the parthenocarpic fruit is seedless. Parthenocarpy naturally occurs in some plants such as banana and pineapple. It is used to increase the quality and productivity of many plants that are grown for fruit. A seedless watermelon is shown in figure 2.

Main Difference - Apomixis vs Parthenocarpy

Figure 2: Seedless Watermelon

Pollination stimulates the production of parthenocarpic fruits in some plants. This process is known as stimulative parthenocarpy. Parthenocarpy that is not stimulated by pollination is known as vegetative parthenocarpy.

Similarities Between Apomixis and Parthenocarpy

Apomixis and parthenocarpy are vegetative propagation methods.
Both apomixis and parthenocarpy use sexual organs of the plant.
No fertilization occurs in both apomixis and parthenocarpy.
Both apomixis and parthenocarpy produce offspring identical to the parents.

Definition

Apomixis: Apomixis refers to a type of asexual reproduction that replaces the normal sexual reproduction in plants.

Parthenocarpy: Parthenocarpy refers to the development of a fruit without prior fertilization.

Significance

Apomixis: Apomixis is the production of seeds without fertilization.

Parthenocarpy: Parthenocarpy is the production of seedless fruits.

Examples

Apomixis: Apomixis occurs in roses and oranges.

Parthenocarpy: Parthenocarpy occurs in banana, pineapple, watermelon.

Importance

Apomixis: Apomixis mimics sexual reproduction of the plant.

Parthenocarpy: Parthenocarpy is induced by the growth regulators such as auxins and gibberellins.

Conclusion

Apomixis and parthenocarpy are two mechanisms involved in the production of seed and fruit in plants. The seeds are produced without fertilization in apomixis. In parthenocarpy, seedless fruits are produced. In both apomixis and parthenocarpy, no syngamy is observed. The main difference between apomixis and parthenocarpy is the product of each type of mechanism in plants.

Reference:

1. Bicknell, Ross A., and Anna M. Koltunow. “Understanding Apomixis: Recent Advances and Remaining Conundrums.” Plant Cell, American Society of Plant Biologists, 1 June 2004, Available here.
2. Spena, Angelo, and Giuseppe Leonardo Rotino. “Parthenocarpy.” SpringerLink, Springer, Dordrecht, 1 Jan. 1970, Available here.
3.“Parthenocarpy.” Parthenocarpy | [email protected], Available here.

Image Courtesy:

1. “Agave angustifolia (Caribbean Agave) in Hyderabad W IMG 8660” By J.M.Garg – Own work (CC BY 3.0) via Commons Wikimedia
2. “Watermelon seedless” By Scott Ehardt – Own work (Public Domain) via Commons Wikimedia