1. Self-pollination
Self-pollination refers to the process where pollen from the same plant's flowers is transferred to its own stigma (either within the same flower or between different flowers of the same plant), completing the pollination process. Self-pollination can occur within different flowers of the same plant or within the same flower.
Characteristics:
Does not rely on external pollinators (such as wind, insects, etc.).
Ensures genetic stability in environments where no external pollination sources are available.
Common in plants that are capable of self-pollination, such as peas, tomatoes, and some fruit trees (like certain varieties of apples and apricots).
Advantages:
Ensures seed production and reproduction even without external pollination.
Stable propagation under certain environmental conditions.
Does not require cross-pollination.
Disadvantages:
Limited genetic diversity, which can lead to inbreeding depression over time if self-pollination is practiced for too long.
2. Self-fruitfulness
Self-fruitfulness refers to plants that are capable of producing fruit and viable seeds even when they only self-pollinate (without external pollen). These plants can successfully produce fruit and seeds after completing self-pollination.
Characteristics:
The plant is able to form fruit without the need for external pollination sources.
These plants can independently reproduce by self-pollination.
Examples:
Some varieties of dragon fruit, tomatoes, peas, etc.
Advantages:
Ensures fruit production even when there are no external pollinators.
Disadvantages:
Limited genetic diversity may result in weaker offspring and lower adaptability.
3. Self-incompatibility
Self-incompatibility refers to a mechanism where a plant's flowers can self-pollinate, but due to genetic factors, the pollen from the same plant is unable to fertilize its own ovules. In other words, although self-pollination occurs, it does not result in the formation of fruit or viable seeds.
Characteristics:
Even if a plant undergoes self-pollination, it will not produce fruit or seeds.
This mechanism is found in some plants to promote genetic diversity by preventing self-fertilization.
Mechanism:
Self-incompatibility is controlled by the plant's genetic system (S-gene) that prevents successful fertilization when the pollen and stigma share the same S-gene. This ensures that only pollen from a different plant can fertilize the flower.
The mechanism is typically controlled by a genetic locus, and if the pollen and stigma are genetically similar, pollination will fail.
Examples:
Some apple varieties, cherries, plums, etc. These plants usually need pollen from a different variety to produce fruit.
Advantages:
Promotes genetic diversity, enhancing the plant population's adaptability and disease resistance.
Disadvantages:
Requires cross-pollination with other plants to set fruit, so it cannot self-reproduce.
Summary:
Self-pollination: Pollen from the same plant pollinates itself but does not necessarily result in fruit.
Self-fruitfulness: Successful fruit and seed production occurs after self-pollination.
Self-incompatibility: Self-pollination does not result in fruit, and the plant requires cross-pollination from another plant.
These different reproductive mechanisms influence the plant's reproductive strategies, genetic diversity, and adaptability.