What is the Difference Between Allogamy and Autogamy

The main difference between allogamy and autogamy is that allogamy refers to the fertilization of a flower by pollen from another flower, especially one on a different plant, while autogamy refers to self-fertilization. Furthermore, cross-pollination occurs in allogamy while self-pollination occurs in autogamy.

Allogamy and autogamy are two forms of fertilization of gametes that occur in flowers. Here, the method of pollination determines the type of fertilization.

Key Areas Covered

1. What is Allogamy
     – Definition, Process, Importance
2. What is Autogamy
     – Definition, Process, Importance
3. What are the Similarities Between Allogamy and Autogamy
     – Outline of Common Features
4. What is the Difference Between Allogamy and Autogamy
     – Comparison of Key Differences

Key Terms

Allogamy, Autogamy, Cross-Pollination, Geitonogamy, Self-Pollination, Xenogamy

What is Allogamy

Allogamy is a type of fertilization that occurs in a flower by the pollen grains of another flower of the same species. Therefore, it is a type of cross-fertilization. Actually, there are two conditions of allogamy known as geitonogamy and xenogamy. Geitonogamy refers to the deposition of the pollen grains of the anther of one flower on the stigma of another flower of the same plant. On the contrary, xenogamy refers to the deposition of pollen grains of the anther of one flower on the stigma of another flower of a different plant in the same species. Therefore, the method of pollination that occurs in allogamy is cross-pollination, which later leads to cross-fertilization.

Figure 1: Cross-Pollination

Allogamy needs the help of external pollinating agents to carry out pollination. Generally, there are two types of pollinating agents: biotic agents (animals and insects) and abiotic agents (wind, water, etc.). Flowers that use biotic agents have unique features such as large size, bright colours, production of nectar, and scent in order to attract the biotic agents to the flower. Moreover, flowers that use abiotic agents for pollination show various adaptations such as their altitude, extending anthers or stigma to the outside of the flower, etc.

What is Autogamy

Autogamy is a type of self-fertilization in which the egg cell in the flower fuses with the sperm cell derived from the anthers of the same flower.  Thus, the flowers that follow autogamy have to undergo self-pollination. Generally, these flowers are neither large nor colourful. The main feature of these flowers is that they do not open at their maturity to expose their reproductive structures to the outside. Additionally, flowers with autogamy contain some other adaptations in the structure of the flower to facilitate self-pollination. These flowers are capable of shedding pollen grains directly onto the stigma. Sometimes, pollination occurs even before the opening of the flower.

Figure 2: Self-Pollination

Moreover, autogamy occurs without any involvement of external pollinating agents. The main importance of autogamy is that it is capable of preserving beneficial genotypes of the plant over generations. However, it produces a less genetically diverse offspring with very low potential to participate in evolution.

Similarities Between Allogamy and Autogamy

• Allogamy and autogamy are two methods of fertilization that occur in the flower.
• Both reproductive structures of the flower, stamen, and pistil participate in each method of fertilization.
• Generally, the method of pollination determines the method of fertilization.
• Flowers show adaptations in order to encourage the type of fertilization they desire.
• Both methods of fertilization show their own benefits towards the plant.

Difference Between Allogamy and Autogamy

Definition

Allogamy refers to the fertilization of a flower by pollen from another flower, especially one on a different plant, while autogamy refers to self-fertilization, especially the self-pollination of a flower. Thus, this explains the main difference between allogamy and autogamy.

Type of Fertilization

Allogamy is a type of cross-fertilization while autogamy is a type of self-fertilization.

Process

In allogamy, the egg cell fuses with a sperm cell produced by the anthers of another plant of the same species while in autogamy, the egg cell fuses with the sperm cell produced by the anthers of the same flower.

Features of Flowers

More, another difference between allogamy and autogamy is that the flowers which undergo allogamy are large and colourful and produce nectar while flowers that undergo autogamy are small and less colourful and usually do not open to expose their reproductive structures to the outside.

Importance

Allogamy participates in evolution by producing new genotypes through genetic recombination while autogamy preserves the existing, beneficial genotypes of the plant over generations. Hence, this is an important difference between allogamy and autogamy.

Conclusion

Allogamy is the cross-fertilization in which the egg cell in a flower fuses with a sperm cell came from a flower on another plant of the same species. Moreover, cross-pollination encourages allogamy. Additionally, the flowers to undergo allogamy are large, colourful and produce nectar to attract animal pollinators. Generally, allogamy takes part in evolution by producing new genotypes. On the contrary, autogamy is the self-fertilization in which the egg cell in the flower fuses with the sperm cell derived from the anthers of the same flower. Furthermore, these flowers do not open, exposing their reproductive structures. Also, they do not attract any pollinating agents. Moreover, autogamy preserves beneficial genotypes of the plant over generations. Therefore, the main difference between allogamy and autogamy is the type of fertilization.

References:

1. “Cross-Fertilization.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 20 July 1998, Available Here.
2. “Self-Fertilization.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 10 Apr. 2016, Available Here.

Image Courtesy:

1. “Cross pollination” By Ali Niaz (CC BY-SA 4.0) via Commons Wikimedia   
2. “Self-pollination(1)” By Jankula00 – Own work (CC BY-SA 4.0) via Commons Wikimedia