Asexual Reproduction of Plants

The flip side of the genetic uniformity of clones is their vulnerability:

Evolutionarily, sexual reproduction is the dominant strategy in higher plants, and for good reason. Meiosis and recombination ensure effective removal of harmful mutations and create the variability necessary for adaptation to changing conditions (Hörandl, 2024). However, asexual reproduction is not a complete ‘evolutionary dead end’. It allows a successful genotype arising from a rare sexual event or mutation to be ‘fixed’ and rapidly multiplied. This is why facultative agamospermy — the ability of plants to reproduce both sexually and asexually depending on circumstances — is widespread in nature (Graham et al., 2014; Bidabadi and Jain, 2020).

This is particularly evident in many weeds, rosette perennials, and species living in extreme high-mountain and Arctic environments, where the short growing season limits the possibilities of sexual reproduction. Moreover, many crops are propagated exclusively vegetatively by humans to preserve valuable varietal traits (Mozet, 2017; Carmel et al., 2024).

Thus, the biological and evolutionary significance of asexual reproduction lies in its serving as an effective tool for the rapid reproduction and dispersal of genetically stable clones well adapted to local conditions. Combined with periodic sexual reproduction, this gives plants unique flexibility: they can both fix successful genotypes and create new genetic diversity for survival in a changing world.

The genetic uniformity of a clone is explained by the fact that during asexual reproduction, all cell divisions leading to the formation of new individuals occur exclusively through mitosis. Mitosis ensures accurate copying of chromosomes and their equal distribution between daughter cells, guaranteeing the preservation of the original genotype (Graham et al., 2014). In contrast, during sexual reproduction, meiosis and recombination occur, leading to the formation of genetically unique zygotes.

In some cases, plants can produce seeds without fertilization (apomixis). The resulting embryos are also clones of the mother plant, although they develop inside the seed (Hörandl, 2024). Such apomictic clones are widespread in many flowering plants, for example in bluegrass (Poa spp.), hawkweed (Hieracium), and dandelion (Taraxacum officinale) (Graham et al., 2014).

The size of clones can vary from a few individuals to giant clonal colonies covering vast areas. A classic example is quaking aspen (Populus tremuloides), where individual clones can cover tens of hectares and include thousands of trunks connected by a common root system. One such clone in Utah (USA) covers more than 40 hectares and weighs an estimated 6,000 tonnes (Mozet, 2017). Similarly, tufted grasses and many perennials (e.g., lily of the valley) form dense clumps that represent clones.

In agriculture, the concept of a clone is of enormous practical importance. Cultivated varieties propagated vegetatively (potato, Jerusalem artichoke, garlic, many fruit and berry crops) are essentially clones. For example, all potato plants of the variety ‘Nevsky’ in the world are the vegetative offspring (clone) of a single original plant selected by the breeder (Mozet, 2017). This ensures uniformity of the crop in morphological and economically valuable traits.

An agronomist and plant grower must consider the properties of clones in practical work:

Thus, the concept of a clone serves as a link between the fundamental biology of asexual reproduction and the applied tasks of crop production, seed production, and biotechnology. Understanding the clonal nature of vegetatively propagated varieties enables the proper planning of breeding programs and plant protection systems.

In the next section, we will examine the classification of different types of asexual reproduction — from sporulation to specialized forms of vegetative reproduction.

This type is characteristic of many algae, fungi (which were previously classified as plants), and for all spore-bearing higher plants — mosses, clubmosses, horsetails, and ferns (Raven et al., 2022; Yakovlev et al., 2005).

Spore is a microscopic, usually unicellular reproductive unit that serves for asexual reproduction and dispersal. In aquatic and many terrestrial plants (e.g., ferns), spores can be motile — zoospores, equipped with flagella (Raven et al., 2022; Graham et al., 2014). Spores of terrestrial plants are generally immotile (aplanospores), have a thick, desiccation-resistant wall made of sporopollenin, and are dispersed by wind or water (Mozet, 2017; Stern et al., 2020).

Spores are formed inside special structures — sporangia (or on specialized hyphae — conidiophores in fungi). A key biological feature is that in all higher plants, spores are formed as a result of meiosis, i.e., they are haploid. From them, not an adult sporophyte plant (as in flowering plants from a seed) germinates, but an asexual generation — the gametophyte (prothallus), which then produces gametes (Stern et al., 2020; Graham et al., 2014). For spore-bearing plants, asexual reproduction by spores serves not only to increase the number of individuals but also for dispersal to new territories. For example, a single fern can produce millions of spores, which the wind carries over vast distances (Mozet, 2017).

Since this article is oriented toward agricultural disciplines and avoids deep systematics, we will not examine in detail the types of sporangia and sporulation mechanisms in different taxa. We will only note that in heterosporous plants (some clubmosses, aquatic ferns, and all seed plants), two types of spores are formed: microspores (small, giving rise to the male gametophyte) and megaspores (large, giving rise to the female gametophyte) (Raven et al., 2022; Yakovlev et al., 2005).

In contrast to spore reproduction, vegetative reproduction does not involve the formation of specialized unicellular spores. A new individual arises from a multicellular fragment of the mother plant — a part of a shoot, root, leaf, or from their modified structures (bulbs, tubers, rhizomes, stolons, brood buds) (Yakovlev et al., 2005; Mozet, 2017). This process is based on the ability of plants to regenerate — to restore a whole organism from its part.

By the origin of the organs involved in vegetative reproduction, we distinguish:

For agricultural education, it is fundamentally important to distinguish between spore and vegetative reproduction because:

In the next section, we will examine the morpho-anatomical foundations and mechanisms underlying asexual reproduction — from cell dedifferentiation to organ and embryoid formation.

In many cases (e.g., during cutting, wounding, or in vitro cultivation), dedifferentiated cells begin to divide actively, forming a mass of unorganized parenchymatous cells called callus (from Latin callus — callosity) (Bidabadi and Jain, 2020; Yakovlev et al., 2005). Callus is essentially a wound tissue in which cells are in a meristematic state and can differentiate into various tissues and organs.

Callus can form both on the cut surface (e.g., in root crops or cuttings) and deep within tissues. Under natural conditions, callus often gives rise to adventitious roots or shoots. In biotechnology, callus cultures are used as a source of cells for microclonal propagation, somatic embryogenesis, and genetic transformation (Bidabadi and Jain, 2020; Meng et al., 2026).

From dedifferentiated cells (callus or individual cells of specialized tissues), further development can proceed along two main pathways: organogenesis or somatic embryogenesis.

Without delving into physiology, it is necessary to note that all the processes described are under hormonal control. The main classes of phytohormones involved in inducing cell division, dedifferentiation, and organogenesis are:

The balance of auxin and cytokinin concentrations in the culture medium or locally in tissues is a key factor determining the morphogenetic pathway (Bidabadi and Jain, 2020; Stern et al., 2020).

In the next section, we will examine the external and internal factors affecting the success of asexual reproduction, as well as the conditions necessary for regeneration.

Abiotic factors are non-living components of the environment that affect plant growth, development, and regenerative capacity.

Biotic factors include influences from living organisms, including pathogens and symbionts.

Pathogens. Bacterial, fungal, or viral infection is one of the main causes of failure in cutting propagation and microclonal propagation. Infected tissues rot, and regeneration does not occur. Therefore, in vegetative propagation, healthy mother stock is used, substrate and tools are sterilized, and fungicides and antibiotics are applied (Bidabadi and Jain, 2020; Carmel et al., 2024).

Symbionts. In some species, the presence of mycorrhizal fungi can positively affect the rooting of microshoots and their subsequent development, but this factor is usually not considered in standard vegetative propagation protocols (Raven et al., 2022).

The success of asexual reproduction depends to a great extent on the condition of the donor plant from which explants (cuttings, leaves, root fragments) are taken (Hartmann et al., 2002).

Age of the donor plant. Tissues of juvenile (young) plants have a significantly higher regeneration capacity than tissues of adult plants that have transitioned to flowering. Juvenile cuttings root more easily and quickly. This is due to the gradual loss of expression of meristematic state genes and the accumulation of repressive epigenetic marks (Bidabadi and Jain, 2020; Meng et al., 2026).

Type and position of the explant. Different types of cuttings are optimal for different species: some root better from semi-hardwood (semi-mature) cuttings, others from green (herbaceous) or hardwood (winter) cuttings (Carmel et al., 2024). The part of the shoot is also important: in many plants, apical cuttings root better than basal ones due to higher endogenous auxin content (Hartmann et al., 2002).

Seasonality (phenological phase). The timing of cutting collection plays a decisive role. In most tree species, the best rooting results are observed at the beginning of shoot growth (spring) or after growth completion (late summer — early autumn), when tissues have maximum carbohydrate content and minimum inhibitors. For many species, cutting collection during the dormant phase (winter cuttings) or, conversely, during active vegetation (green cuttings) is optimal (Carmel et al., 2024; Hartmann et al., 2002).

Endogenous hormonal status. The level of endogenous auxins, cytokinins, and inhibitors (abscisic acid, phenolic compounds) in the explant tissues directly affects regeneration capacity. A high auxin/inhibitor ratio promotes rooting, while a high cytokinin/auxin ratio promotes shoot formation (Bidabadi and Jain, 2020; Carmel et al., 2024).

The formation of new organs (roots, shoots, tubers) requires significant expenditure of plastic and energy resources. Therefore, explants (cuttings, rhizome fragments, bulbs) must have sufficient reserves of carbohydrates (starch, sugars) and nitrogenous compounds. In many species, cuttings taken from well-lit and healthy plants root more successfully. In industrial cutting propagation, pre-treatment called ‘etiolation’ — shading the shoots — is sometimes used, which promotes starch accumulation and increases auxin content (Hartmann et al., 2002).

In the next section, we will examine the practical aspects of managing asexual reproduction in agronomy: from traditional methods (cuttings, layering) to modern biotechnological techniques (microclonal propagation, use of growth regulators).

All traditional methods are based on separating a part from the mother plant, which then roots and develops into an independent individual — a clone.

The use of techniques to manage asexual reproduction addresses the following tasks:

Thus, managing asexual reproduction is a powerful tool in modern crop production, allowing not only to preserve and propagate valuable genotypes but also to significantly increase the efficiency of agricultural production. The combination of traditional agronomic techniques with cutting-edge biotechnological methods opens prospects for creating sustainable and productive agroecosystems.

In the next, concluding section, we will summarize and consider the connection of asexual reproduction with other branches of botany and agronomy.