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Dandelion ( Taraxacum ) attracts pollinators, but this is not necessary for seed formation

Under Agamospermy is the formation of seeds without sexual processes. It is thus a form of apomixis (asexual reproduction). If pollination is required as a trigger, one speaks of pseudogamy . The resulting daughter organisms are genetically identical to the mother plant due to the lack of fertilization by another individual ( clones ).

Since fertilization is no longer possible with some forms of agamospermia, Ernst Mayr's species concept also runs into problems, because he defines species because they are reproductively isolated populations. If there is no more fertilization, then each individual is reproductively isolated, i.e. its own species. A switch to other species concepts such as differentiation through morphological features (morpho-species) may create a little order, but in cases like the Taraxacum dandelion it also leads this to hundreds of small species ("agamospecies").

In contrast to self-pollination , agamospermia does not lead to inbreeding depression , since the genetic effects leading to it, especially unfavorable homozygous alleles for recessively inherited disadvantageous traits, will hardly occur in agamosperm individuals, since the gene combination of the maternal organism was presumably favorable in successful individuals (low genetic Load or burden). This corresponds to the initial situation also for regularly self-pollinating species. However, many researchers still suspect adverse effects due to new mutations if recombination no longer occurs in the course of reproduction ( Muller's ratchet ); however, these may only have a very long-term effect. In agamospermia in the narrower sense, however, in contrast to vegetative reproduction , a stage with meiosis and recombination may have been retained (unisexual reproduction, as opposed to asexual reproduction), so that the corresponding consequences do not necessarily have to occur.

Since the variability is lower in agamosperm species, they can multiply particularly quickly under environmental conditions that happen to be particularly favorable for a particular individual. They are therefore often good colonizers in newly created habitats. Many agamosperm species are found in areas that were free of vegetation during the ice ages .

Agamospermia is known from at least 34 plant families , such as the rose family ( lady's mantle , blackberries etc.), the daisy family ( hawkweed , taraxacum etc.) and the sweet grasses ( panicle grasses ).

In the mechanisms, a distinction is sporophytic from the gametophytic the latter being subdivided into apospory and diplospory Agamospermy.

Sporophytic agamospermia

In sporophytic agamospermia, the embryo does not arise through fertilization of the embryo sac, but in the sporophytic (maternal) nucellus tissue that surrounds the female gamete and is usually used to nourish the seeds. In order to form a nucellus embryo, pollination is often necessary as a chemical stimulus (pseudogamy).

Sporophytic agamospermia is facultative and can even run parallel to sexual seed formation. In the case of the genus Citrus , for. B. thus to a polyembryony in which several embryos per seed arise, partly sexually, partly asexually.

Further examples of sporophytic agamospermia are the genera of the Opuntia ( Opuntia ) and the cabbage rose ( Nigritella ).

Gametophytic agamospermia

In gametophytic agamospermia, meiosis does not occur in the embryo sac mother cell , so that the resulting multinucleated embryo sac is polyploid as a whole. A diploid daughter organism then develops from one of the thus diploid embryo sac nuclei, without fertilization by a male gamete . If this embryo sac core corresponds to the egg cell, then parthenogenesis (embryo formation from an unreduced egg cell) is present, otherwise one speaks of "apogamy".


The golden cinquefoil Potentilla aurea can also reproduce from seeds without having to fertilize an egg cell.

In aposporia, the embryo sac is formed in the nucellus, but not in the actual spore-forming tissue ( archespor ), but elsewhere. The remaining ("normal") embryo sac can also lead to parallel sexual fertilization. Pollination is often necessary (pseudogamy) in order to obtain a triploid endosperm (from a diploid embryo sac nucleus instead of two haploid nuclei, as is normal).

In the meadow bluegrass ( Poa pratensis ) 5 genes are needed to produce seeds without fertilization. Among other things, these are responsible for suppressing meiosis. The apospory is also in the cinquefoils and in the hawkweed -Untergattung Pilosella common.


In diplosporia, the embryo sac arises, as is normal, in the archespora. There, however, no reduction division is carried out, but the embryo sac mother cell itself grows to the next generation. Since sexual reproduction is no longer possible, this form is mandatory.

Diplosporia is mainly found in the sunflower family , such as the Taraxacum dandelion , the cat's paw ( Antennaria ) or the real hawk herbs (subgenus Hieracium ).

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