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Parthenogenetic development of sex cells without fertilization.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



various forms of asexual reproduction by animals and plants. In a more common, narrow sense, apomixis is the formation of an embryo without fertilization. In apomixis the embryo develops not from a zygote, but directly from an unfertilized egg cell (parthenogenesis) or—in higher plants—from the cell of the gametophyte, from the embryonic sac (apogamy), and even from the somatic cells of a seed bud. Apomixis is known in the form of parthenogenesis in worms, insects, fish, and reptiles. However, it is more widespread among plants. Apomixis, or asexual seed reproduction (agamospermy), is especially frequent among angiosperms. There are several thousand apomictic species among 300 genera of angiosperms, belonging to 80 families. These include such common, widespread plants as grasses (60 genera), the composite family (28 genera), the rose family (15 genera), and the rue family (13 genera).

Apomixis can be autonomous—in which case both the embryo and endosperm form without fertilization—and mentoral (pseudogamic or stimulatory)—in which case the embryo is formed from an unfertilized egg cell, but its development is stimulated by the fertilization of the embryonic sac, which gives rise to the endosperm. Apomixis may be induced experimentally by some factors (induced apomixis). Apomixis sometimes manifests itself sporadically in certain organisms (facultative apomixis) or is the basic and even sole means of reproduction (obligatory apomixis).

As a rule, apomictic species occupy vast areas without showing any sign of becoming extinct (many species of hawkweed, dandelion, lady’s mantle, cinquefoil, meadow grass, European dewberry, and others). Apomixis is successfully utilized in the breeding of citrus fruits, figs, fodder grasses, and other plants. It can be used in producing hybrid corn seeds and other crops from apomictic haploids by means of doubling the number of their chromosomes. Especially important is the use of apomixis with fruit bushes and other woody bushes for which the development of homozygous strains by lengthy self-pollination in six to seven generations is practically impossible. Apomixis can be used to enhance crossbred vigor since it gives rise to a relatively constant progeny which conserves the particularities of the primary form. In the USA and Britain this is the basis of producing on an industrial scale uniform and hardy stock grown from apomictic seedlings of certain apple species. In California, seedlings from apomictic seed buds are used to replace degenerating and weakened clones of citrus trees, which are usually reproduced vegetatively.


Khokhlov, S. S. Perspektivy evoliutsii vysshikh rastenii. Saratov, 1949.
Khokhlov, S. S. “Apomiksis: klassiflkatsiia i rasprostranenie u pokrytosemennykh rastenii.” In Uspekhi sovremennoi genetiki, vol. 1. Moscow, 1967.
Maheshwari, P. Embriologiia pokrytosemennykh. Moscow, 1954. (Translated from English.)
Poddubnaia-Arnol’di, V. A. Obshchaia embriologiia pokrytosemennykh rastenii. Moscow, 1964.
Petrov, D. F. Geneticheski reguliruemyi apomiksis. Novosibirsk, 1964.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
In apomicts, the development of an unreduced egg in the female gametophyte is normal; therefore, 2n + n fertilization should occur at a higher frequency in apomicts than in sexual plants.
The remaining species reproduced primarily by apomixis and these data demonstrated that apomicts do not necessarily have high seed set.
Environmentally induced variation in facultativeness and fertility is common among apomicts (Asker and Jerling, 1992).
Meiosis and aposporous embryo sac formation are partially to fully superimposed in most aposporous apomicts, which also suggests an asynchrony of duplicate developmental pathways.
Inheritance studies indicated a single-locus model of genetic control of apomixis in the signalgrass-palisadegrass-ruzigrass agamic complex (Ndikumana, 1985; Valle et al., 1994; Valle and Savidan, 1996): tetraploid apomicts are simplex for a dominant allele (Aaaa) at the putative "apomixis locus," sexuals being homozygous recessive at the locus and either diploid (aa) or tetraploid (aaaa).
decumbens hybrids, which were expected to segregate for edaphic adaptation because of the typically high heterozygosity level of apomicts such as B.
Inferred Population Genetical Evidence.--Strict apomicts evolve separately along clonal lines.
In an earlier study (Roy and Rieseberg, 1989), electrophoresis of progeny arrays from Arabis holboellii collected at the Cement Creek site revealed no recombination, suggesting that the clonal variation uncovered there may have resulted from polyphyletic origin of the apomicts from sexual parents combining different alleles.
True apomicts identified in the first Class 2-[F.sub.x] cycle should also produce white (or red) Class 2-[F.sub.2y] seed in the second cycle.
Tetraploid bahiagrass plants are generally obligate apomicts, and improvement has been hampered by the lack of stable, sexual tetraploid types.
Hybrids with progeny exhibiting partial uniformity and a degree of variability were classified as facultative apomicts, and hybrids with completely variable progeny were scored as sexual.