The term self-pollination or direct or homoclinic pollination means that when a plant flowers from their own pollen dusted be. These can only be hermaphroditic flowers. It can happen directly, spontaneously (obligatory) or indirectly (optional) due to environmental conditions.
The self-pollination is often done when closing a flower if the stamens the scar then touch. If the targeted self-pollination takes place before the flower opens, this is also known as celestogamy . The other case, pollination in the open flower, is called chasmogamy .
A special, rare type of chasmogamous, indirect self-pollination is rain pollination , ombrophilia (ombrogamy), a flower wetted by rain. When it rains, the flower bowls fill with water and the pollen is transferred from the anthers to the stigma. This is not the same as ombrochory , the spreading of seeds by raindrops.
The self-fertilization , autogamy (from ancient Greek αὐτός autós "self" and γάμος Gamos "marriage, marriage, marriage"), is the generic term for self-pollination. The opposite of self-fertilization is cross-fertilization (allogamy) (cross- pollination ; xeno- and geitonogamy ). If autogamy leads to fertilization, this is called autocarpy . The simultaneous ripening of stamens and stigmas of a hermaphrodite flowering plant, so that self-pollination becomes possible, is called homogamy , the other case is dichogamy .
Self-fertilization and neighboring fertilization (geitonogamy) are genetically equivalent; Endogamy (autogenetic pollination, inbreeding) (inbreeding). Geitonogamy and autogamy are grouped under individual or self- pollination (idiogamy, inbreeding).
Self-pollination can be particularly beneficial for pioneer plants that are spread by long-distance transport. This gives the plants the opportunity to build up a large population even as a single individual . Habitats in which self-pollinating plants are very common are mainly islands ( island flora ) and extreme locations with missing pollinators ( desert / arctic ). The proportion of self-pollinating plants is very high, especially on islands. Some of these plants allow cross- pollination at an early stage of their flowering and only switch to self-pollination in the final stages of flowering.
Self-pollination reduces genetic variability and can lead to less healthy offspring due to inbreeding depression .
Therefore, many plant species have mechanisms that make self-pollination less likely or even prevent it:
- Genetic self-incompatibility : In this case, genetic factors prevent self-fertilization.
- Dichogamy: Temporal separation of the production of male and female gametes , accordingly there are pre- male ( proterandry ) and pre- female flowers ( proterogyny ). Simultaneous maturity is called homogamy .
- Herogamy : spatial separation of the male and female sexual organs within a flower.
Dichogamy and herogamy cannot always prevent pollination within a flower. Therefore, many species have developed further avoidance mechanisms.
Such incompatibility systems are often also morphologically recognizable:
- Heteromorphism : a well-known example is anisostyly or heterostyly (different styling ) or enantiostyly (crooked styling).
- Another example is adynamandria , at- , autatrygia , sterility with its own pollen or the inability of male flower organs to function, e.g. B. Hedychium coccineum .
- Flexistyly : Here a movable stylus prevents self-pollination. Depending on the degree of ripeness of the stamens, the stylus moves up or down.
- Heterodynamy or pseudo-hybridism : Term for apparently hermaphroditic flowers with unevenly developed (unevenly) to functionless anthers or stigmas.
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