Self-pollination and cross-pollination are two different mechanisms of pollination in plants. Here are five key differences between self-pollination and cross-pollination:
Source of Pollen:
Self-Pollination: In self-pollination, the pollen from the anther of a flower is transferred to the stigma of the same flower or another flower on the same plant. It involves the transfer of pollen within the same individual plant.
Cross-Pollination: In cross-pollination, the pollen is transferred from the anther of one flower to the stigma of a flower on a different plant. It involves the transfer of pollen between different individuals of the same species.
Genetic Variation:
Self-Pollination: Self-pollination tends to result in less genetic variation because it involves the combination of genetic material from the same plant. Offspring produced through self-pollination are genetically similar to the parent plant.
Cross-Pollination: Cross-pollination promotes genetic diversity as it involves the exchange of genetic material between different plants. This can lead to offspring with a combination of traits from both parent plants.
Mechanisms to Prevent Selfing:
Self-Pollination: Some plants have mechanisms to prevent self-pollination, such as physical barriers that separate the male and female reproductive organs in a flower. Others may have mechanisms like self-incompatibility, where the plant rejects its own pollen.
Cross-Pollination: Cross-pollination serves as a mechanism to promote genetic diversity. Many plants have adaptations that encourage cross-pollination, such as producing attractive flowers to attract pollinators or having separate male and female flowers.
Dependence on Pollinators:
Self-Pollination: Self-pollination can occur without the involvement of external agents like wind or pollinators. Some plants are capable of self-pollination through mechanisms like gravity, mechanical pressure, or simple contact between male and female reproductive organs.
Cross-Pollination: Cross-pollination often relies on external agents, such as insects, birds, wind, or water, to transfer pollen between flowers. The presence of pollinators is crucial for the success of cross-pollination.
Advantages and Disadvantages:
Self-Pollination: Self-pollination is advantageous in stable environments where the plant is well-adapted. It ensures reproductive success even in the absence of pollinators. However, it may lead to a lack of genetic diversity and limit the ability of the plant to adapt to changing conditions.
Cross-Pollination: Cross-pollination promotes genetic diversity, increasing the chances of producing offspring with beneficial traits. It allows for adaptation to changing environmental conditions. However, it is dependent on external factors like pollinators and may be less efficient than self-pollination in certain circumstances.
In summary, self-pollination involves the transfer of pollen within the same plant, leading to less genetic variation, while cross-pollination involves the transfer of pollen between different plants, promoting genetic diversity. The mechanisms, genetic outcomes, dependence on external agents, and advantages/disadvantages differ between these two pollination methods.