Plant Reproduction

Last updated: June 04, 2026EspañolРусский

Plant reproduction is a fundamental property of all plant organisms, consisting of the ability to produce new offspring, ensuring the continuity and persistence of the species. In essence, reproduction is the process of producing similar offspring, which not only maintains the species through evolutionary time but also increases the number of individuals, disperses them, and occupies new territories (Andreeva & Rodman, 2002; Barrett, 2017).

However, it is important to distinguish between two closely related but not identical concepts: reproduction and multiplication (or propagation). Reproduction is the general ability of an organism to produce offspring, which may be similar to the parent (e.g., in vegetative propagation) or pass through alternating phases of the life cycle (e.g., in ferns, where a spore gives rise to a gametophyte unlike the parent plant). Propagation is the process that leads to an increase in the number of individuals of a given species. In most cases these two phenomena coincide, but not always: for example, the formation of a spore in a fern is a stage of reproduction, but the spore itself is not yet a new individual; it will only give rise to a new plant after germination (Serebryakova et al., 2006).

From a biological perspective, reproduction solves three key tasks. First, it ensures the preservation of the species over time, compensating for natural mortality of individuals. Second, it creates opportunities for dispersal – colonising new habitats, which is critically important for survival in changing environmental conditions. Third, reproduction, especially sexual reproduction, is the main mechanism for generating genetic diversity, which serves as the "raw material" for natural selection and evolutionary change (Graham et al., 2014; Mauseth, 2016).

Depending on how offspring are formed and whether sex cells (gametes) are involved, the diversity of plant reproduction methods can be divided into three main types: vegetative, asexual (spore-based), and sexual.

The key distinction among these types relates to the concept of homophasic and heterophasic reproduction (Serebryakova et al., 2006). In homophasic reproduction, a new individual arises directly from a part of the parent plant (e.g., from a rhizome or cutting) and initially finds itself in the same life cycle phase as the parent. This type is characteristic of vegetative propagation and part of asexual reproduction (e.g., spore formation by mitosis in some algae). In heterophasic reproduction, there is an obligatory alternation of two phases – the sporophyte (diploid) and the gametophyte (haploid), which are morphologically dissimilar. This is a fundamental feature of sexual reproduction in higher plants, where a spore (product of meiosis) gives rise to the gametophyte, and fertilisation returns to the diploid sporophyte (Beck, 2010; Becker et al., 2025).

In botany, the term "alternation of generations" is used to describe this phenomenon. The gametophyte is the sexual generation on which gametes (eggs and sperm) are formed. The sporophyte is the asexual generation on which spores are formed via meiosis. In different plant groups, the ratio and appearance of these two generations can vary greatly: from the dominance of the gametophyte in mosses to the absolute dominance of the sporophyte in angiosperms, where the gametophyte is represented by only a few cells (Raven et al., 2013; Evert, 2013).

Thus, plant reproduction is not merely a process of creating new organisms, but a complex, evolutionarily shaped system that includes various strategies: from rapid cloning of successful genotypes (vegetative propagation) to generating genetically unique offspring capable of adapting to variable environmental conditions (sexual reproduction). In the following sections, we will examine each of these methods, their mechanisms, biological significance, and role in the evolution of the plant kingdom.

1. Biological and evolutionary significance of plant reproduction

Reproduction is not just a mechanism to increase the number of individuals, but a key factor that determined the very existence and evolutionary success of plants on Earth. Its significance unfolds at several levels: from the survival of an individual species to the global functioning of the biosphere.

1.1 Evolutionary origin: from water to land

The ancestors of modern plants – green algae (specifically charophytes) – lived in aquatic environments where reproduction was closely tied to the presence of water. In most algae, both gametes (eggs and sperm) and zoospores were motile and moved using flagella, and fertilisation required an aquatic medium (Graham et al., 2014). However, the transition to life on land, which occurred about 450–500 million years ago, required a radical restructuring of reproductive strategies (Becker et al., 2025).

A key evolutionary acquisition of land plants (embryophytes) was the emergence of alternation of generations with a dominant diploid sporophyte. In most algae, only the zygote is diploid and it immediately divides by meiosis. In land plants, the zygote develops into a multicellular sporophyte, which allowed:

Protection of the developing embryo: the sporophyte receives nutrition from the maternal gametophyte (which gave the name "embryophytes" – "plants with an embryo").
Increase in offspring numbers: one sporophyte can produce millions of spores resistant to desiccation.
Division of functions: the gametophyte became specialised for sexual reproduction, while the sporophyte specialised in dispersal and biomass accumulation (Raven et al., 2013; Beck, 2010).

Simultaneously, structures evolved that made fertilisation independent of free water. In seed plants, sperm lost their flagella (becoming non-motile) and are transported to the egg via a pollen tube (siphonogamy). The pollen grain is a reduced male gametophyte protected by a tough wall of sporopollenin – the most resistant known biopolymer (Evert, 2013; Mauseth, 2016).

1.2 Importance for survival and adaptation

Reproduction provides two main evolutionary and ecological advantages: reproductive assurance and genetic variability.

Reproductive assurance is especially important when pollination is difficult (e.g., at low population density or absence of pollinators). Many plants can self-pollinate or reproduce vegetatively, guaranteeing offspring even under unfavourable conditions. However, the price is reduced genetic diversity (Barrett, 2017).
Genetic variability is generated primarily by sexual reproduction. Gene recombination during meiosis (crossing over and independent assortment of chromosomes) and random gamete fusion during fertilisation produce unique genotypes. This variability provides the material for natural selection and allows populations to adapt to changing environmental conditions, diseases, and pests (Graham et al., 2014; Evert, 2013).

Vegetative propagation, in contrast, allows rapid colonisation of suitable habitats by "cloning" a successful genotype. For example, aspen groves (Populus tremuloides) can be a single clone occupying tens of hectares and persisting for thousands of years via root suckers (Mauseth, 2016).

1.3 Role in the biosphere and agronomy

Plant reproduction has planetary significance. It is thanks to the ability for seed reproduction and efficient dispersal that angiosperms became the dominant group in most terrestrial ecosystems. Flowers and inflorescences that attract pollinators, and diverse fruits and seeds dispersed by wind, water, or animals – all these are evolutionary adaptations that increase reproductive efficiency (Simpson, 2019; Bell, 1991).

From an agronomic perspective, understanding the types of reproduction and their evolutionary significance underpins modern crop production:

Seed reproduction allows the production of hybrid seeds with improved traits (yield, disease resistance) through controlled crossing.
Vegetative propagation (cuttings, layering, grafting) enables the preservation of valuable fruit and ornamental cultivars without trait segregation.

Thus, plant reproduction is not just a biological process, but a crucial evolutionary and ecological mechanism. It provides both the stability of species existence (via vegetative reproduction and self-pollination) and its plasticity and capacity for evolution (via cross-pollination and genetic recombination). The following sections will be devoted to specific methods and mechanisms of these processes.

2. Classification of plant reproduction methods

The diversity of plant reproduction methods is traditionally grouped into three main types: vegetative, asexual (spore-based), and sexual. This classification is based on two criteria: (1) the type of cells (or tissues) used to form a new individual, and (2) the presence or absence of gamete fusion (Serebryakova et al., 2006; Andreeva & Rodman, 2002).

Here we briefly characterise each type and then present a more detailed scheme accounting for alternation of generations.

2.1 Vegetative reproduction

Main page: Vegetative reproduction

Vegetative reproduction is the increase in the number of individuals through the detachment of viable parts of the vegetative body of the plant. Such parts can be rhizomes, tubers, bulbs, stolons (runners), root suckers, as well as special brood buds or even leaves (Serebryakova et al., 2006; Mauseth, 2016).

A key feature of vegetative reproduction is that all daughter individuals are clones, i.e., genetically identical to the mother plant because they are formed by mitotic divisions. This provides two major advantages:

rapid colonisation of suitable habitats;
preservation of a successful gene combination (e.g., in cultivated varieties).

A disadvantage is the lack of genetic diversity, making the clone vulnerable to changing environmental conditions or specialised pathogens (Graham et al., 2014; Barrett, 2017).

In nature, vegetative reproduction is widespread among herbaceous perennials (couch grass, lily of the valley, strawberry), many shrubs, and even trees (e.g., aspen forms huge clonal colonies). In agriculture and horticulture, this method is used to propagate potato varieties, tulips, fruit and berry crops (Mauseth, 2016).

2.2 Asexual reproduction (spore-based)

Main page: Asexual reproduction

In the botanical tradition, asexual reproduction refers to the formation of new individuals from specialised single-celled initials – spores that arise mitotically (mitospores). This type of reproduction is characteristic of many algae and fungi, but is rare in higher plants (as an exception, mitospore formation in some ferns) (Serebryakova et al., 2006; Graham et al., 2014).

However, in a broad sense, the term "asexual reproduction" is often used to denote reproduction by spores formed by meiosis (meiospores). This is a key stage in the life cycle of all higher plants, but it is part of the sexual process, not an independent asexual method. To avoid confusion, modern biology distinguishes:

mitospores (product of mitosis) – enable true asexual reproduction;
meiospores (product of meiosis) – serve for alternation of generations and belong to the sexual cycle (Serebryakova et al., 2006; Evert, 2013).

In the vast majority of higher plants (from mosses to angiosperms), spores are formed meiotically and give rise to the gametophyte. Therefore, speaking of "asexual reproduction" in flowering plants in the strict sense is incorrect – they have no mitospores. Their seed reproduction is part of the sexual process (Raven et al., 2013).

2.3 Sexual reproduction

Main page: Sexual reproduction

Diagram of flower structure — ©איתן פרמן commons.wikimedia.org CC BY-SA 3.0
Main parts of a flower of an angiosperm.
1 – perianth, 1a – calyx, 1b – corolla, 2 – stamen, 2a – filament, 2b – anther, 3 – pistil style, 4 – ovary, 5 – stigma.

Sexual reproduction is based on the fusion of two specialised cells – gametes, which leads to the formation of a zygote. Gametes are formed on the gametophyte and, unlike spores, cannot develop independently without fertilisation (Graham et al., 2014).

In plant evolution, several forms of the sexual process are distinguished (Serebryakova et al., 2006; Andreeva & Rodman, 2002):

Isogamy – fusing gametes are identical in form and size but physiologically different ("+" and "–"). Found in many algae.
Heterogamy (anisogamy) – gametes differ in size, but both are motile. A rare form.
Oogamy – gametes are markedly different: a large, non-motile egg (female gamete) and a small, motile sperm (or non-motile spermatium). Characteristic of most higher plants.

In seed plants (gymnosperms and angiosperms), the male gametophyte is reduced to a pollen grain, and the female gametophyte to an embryo sac (in angiosperms). Fertilisation occurs without free water: the pollen tube delivers spermatia to the egg. In angiosperms, a unique process arises – double fertilisation, where one sperm fuses with the egg (forming a zygote), and the second fuses with the central cell of the embryo sac (forming triploid endosperm). This is a key evolutionary acquisition of flowering plants (Evert, 2013; Beck, 2010).

2.4 Unified scheme: homophasic and heterophasic reproduction

To unite all three types of reproduction into a logical system, the Italian scientist E. Battaglia (1963) proposed distinguishing two fundamentally different pathways of reproduction (Serebryakova et al., 2006):

Homophasic reproduction – a new individual arises from a part of the parent organism without switching to another life cycle phase. Gametophyte gives rise to gametophyte, sporophyte to sporophyte. This includes vegetative reproduction (spread by rhizomes, tubers, brood buds) and asexual reproduction by mitospores (in some algae and fungi). Genetically, the offspring are identical to the parent (clone).
Heterophasic reproduction – obligatory alternation of two generations: the sporophyte (diploid) and the gametophyte (haploid). The meiospore (product of meiosis) gives rise to the gametophyte, and the zygote (product of gamete fusion) gives rise to the sporophyte. This is the basis of sexual reproduction in all higher plants. It is heterophasic reproduction that generates genetic diversity (Serebryakova et al., 2006; Barrett, 2017).

Thus, the classification of plant reproduction methods can be represented by the following scheme:

Plant reproduction:

Homophasic reproduction (cloning):
- Vegetative reproduction (by parts of the vegetative body)
- Asexual reproduction by mitospores (in algae, fungi)
Heterophasic reproduction (alternation of generations):
- Sexual reproduction (meiospore formation → gametophyte → gametes → zygote → sporophyte)

In angiosperms, heterophasic reproduction reaches its highest complexity: the male and female gametophytes are reduced to a few cells and reside within the flower, and fertilisation culminates in the formation of a seed and fruit. At the same time, many flowering plants retain the ability for homophasic (vegetative) reproduction, providing them with evolutionary flexibility.

In the following sections, we will examine in detail the specific mechanisms of each of these processes – from flower structure and gametophyte development to pollination, fertilisation, and seed formation.

3. Plant life cycles

Understanding life cycles is the key to comprehending how plant reproduction is organised. Unlike animals, where the adult is diploid and only the sex cells (gametes) are haploid, plants exhibit a regular alternation of two independent (or semi-independent) multicellular generations: the diploid sporophyte and the haploid gametophyte. This phenomenon is called alternation of generations (alternation of generations) (Raven et al., 2013; Evert, 2013).

3.1 Definition of key concepts

Scheme of gametophyte and gamete evolution in plants — CC BY 4.0
Comparison of gametophyte and gamete morphology in the green alga <span lang="la" class="biological-name">Chlamydomonas</span>, moss, fern, gymnosperm, and angiosperm.
The diagram shows: in algae – isogamy, motile gametes; in non-seed plants (moss, fern) – multicellular gametophyte with antheridia and archegonia, flagellated sperm; in seed plants – reduction of the gametophyte to a pollen grain (male) and embryo sac or archegonium (female), loss of flagella in spermatia.

Before moving to specific examples, let us clearly define four key terms that underlie any plant life cycle (Serebryakova et al., 2006; Andreeva & Rodman, 2002).

Sporophyte – the diploid (2n) generation. On the sporophyte, within specialised organs – sporangia – haploid spores (meiospores) are formed via meiosis. The sporophyte is the plant we usually see: a tree, grass, fern, flower. In angiosperms and gymnosperms, the sporophyte is the dominant, large, independent generation.
Gametophyte – the haploid (n) generation. The gametophyte develops from a spore and produces sex cells – gametes (eggs and sperm or spermatia) by mitosis (not meiosis!). In different plant groups, the gametophyte can range from a relatively large, independent organism (mosses, ferns) to a microscopic one completely dependent on the sporophyte (seed plants).
Spore – a haploid cell formed by meiosis on the sporophyte. It can germinate into a new gametophyte without fusing with another cell. Spores are often covered with a tough wall of sporopollenin, making them resistant to desiccation and capable of wind dispersal (in mosses, ferns). In seed plants, spores lost the dispersal function and remain inside the sporophyte (microspores and megaspores).
Gamete – a haploid sex cell formed by mitosis on the gametophyte. Gametes are of two types: male (sperm – motile, flagellated; or spermatia – non-motile) and female (egg cells). Fusion of two gametes (fertilisation) is required to form a zygote.

3.2 Evolution of life cycles: from water to land

In most green algae (e.g., in Ulothrix or Chlamydomonas), the life cycle is haplobiontic (or zygotic): the vegetative body is haploid, only the zygote is diploid, and it immediately divides by meiosis, restoring the haploid state. This type is considered ancestral (Graham et al., 2014; Beck, 2010).

During the transition to terrestrial life, two key evolutionary events occurred:

Delayed meiosis: the zygote began to divide mitotically, forming a multicellular diploid sporophyte.
Reduction of the gametophyte: in the course of evolution, the haploid generation became increasingly smaller and more dependent on the sporophyte.

In modern land plants (from mosses to angiosperms), the life cycle is diplohaplobiontic (or sporic) with dominance of one or the other phase (Serebryakova et al., 2006; Evert, 2013). Depending on which generation is larger and more independent, three main types are distinguished (see table).

Table. Sporophyte – gametophyte relationship in different plant groups.

Plant group	Sporophyte (2n)	Gametophyte (n)	Life cycle type
Mosses (Bryophyta)	Small, depends on gametophyte, short-lived	Large, independent, photosynthetic	Gametophyte dominant
Ferns (Polypodiophyta)	Large, independent, dominant	Small (prothallus), independent, short-lived	Sporophyte dominant, gametophyte independent
Gymnosperms (Pinophyta, Cycadophyta and others)	Large, woody, dominant	Microscopic, develops inside spore and on sporophyte	Sporophyte dominant, gametophyte parasitic
Angiosperms (Magnoliophyta)	Large, dominant	Highly reduced (pollen grain – 3 cells; embryo sac – 8 nuclei/7 cells)	Sporophyte dominant, gametophyte completely dependent

3.3 Diversity of life cycles: examples

Comparison of reproduction cycles of non-seed and seed plants — CC BY 4.0
Simplified scheme of reproductive modes in non-seed and seed plants.
In non-seed plants (left), the gametophyte (prothallus) is free-living, sperm are motile and require water. In seed plants (right), the gametophyte is reduced and protected by sporophyte tissues, spermatia are non-motile and delivered by a pollen tube. The role of reactive oxygen species (ROS) at key stages is indicated.

Mosses (Bryophyta): gametophyte dominance

In mosses (e.g., Polytrichum), the green, photosynthetic plant we see is the gametophyte. It develops from a spore and has rhizoids, a stem, and leaves. On the gametophyte, antheridia (male reproductive organs) and archegonia (female) are formed. Sperm (motile, flagellated) reach the egg via water. From the fertilised egg (zygote), a small sporophyte grows, remaining attached to the gametophyte and nourished by it. The sporophyte is a capsule on a seta, inside which spores are formed by meiosis. Spores are dispersed and give rise to new gametophytes (Evert, 2013; Raven et al., 2013). Thus, in mosses, the gametophyte is the dominant, independent generation, while the sporophyte is temporary and dependent.

Ferns (Polypodiophyta): independent but small gametophyte

Diagram of alternation of generations in a fern — commons.wikimedia.org CC BY-SA 3.0
Alternation of generations in ferns: sporophyte (large plant) and gametophyte (small prothallus).
The diagram clearly shows the key stages: spore formation (meiosis), dispersal, gametophyte (prothallus) development, gamete formation (mitosis), fertilisation, and new sporophyte formation.

In ferns, the large, dissected plant is the sporophyte. On the underside of its leaves (fronds), sporangia are formed, often grouped into sori. Within the sporangia, haploid spores are produced after meiosis. Spores are released and germinate into a very small (thumbnail-sized) green, heart-shaped plant – the prothallus. This is the gametophyte of the fern. The prothallus lives independently, photosynthesises, and attaches to the soil with rhizoids. On its underside, antheridia and archegonia develop. Sperm (motile) swim to the egg via water. From the zygote, a new large sporophyte grows (initially feeding on the gametophyte but quickly becoming independent). Here both generations – sporophyte and gametophyte – are capable of independent living, but the sporophyte is much larger and longer-lived (Graham et al., 2014; Mauseth, 2016).

Seed plants (Spermatophyta): extreme reduction of the gametophyte

Diagram of angiosperm life cycle — ©العربيَّة commons.wikimedia.org CC BY-SA 3.0
Life cycle of a flowering plant: from seed to adult sporophyte and back.
The diagram shows all stages: seed germination, sporophyte growth, flowering, formation of male and female gametophytes, pollination, double fertilisation, seed and fruit development.

In seed plants (gymnosperms and angiosperms), the most extreme reduction of the gametophyte occurred. The male gametophyte is represented by the pollen grain, which develops from a microspore. In angiosperms, the mature pollen grain consists of just three cells (one vegetative and two spermatia). The female gametophyte in gymnosperms is multicellular (primary endosperm) with archegonia; in angiosperms, it is the embryo sac, usually of seven cells (eight nuclei), including the egg cell and the central cell.

Diagram of seed and embryo development in a flowering plant — ©Chiswick Chap commons.wikimedia.org CC BY-SA 4.0
Embryo and endosperm development in a dicot (example <span lang="la" class="biological-name">Capsella</span>).
The diagram shows successive stages from fertilised embryo sac to mature seed: zygote, globular and heart-shaped embryo, cotyledon formation, endosperm development.

The most important adaptation of seed plants is pollination: the transfer of a pollen grain (male gametophyte) to the ovule (female gametophyte) by wind or animals. Water is not required for fertilisation. After pollination, the pollen tube delivers spermatia to the egg. The zygote develops into an embryo, and the ovule turns into a seed, protected by a seed coat and often supplied with stored nutrients (endosperm) (Evert, 2013; Beck, 2010).

In angiosperms, a unique phenomenon arises – double fertilisation: one sperm fuses with the egg (forming a diploid zygote), and the second fuses with the central cell (forming triploid endosperm). This angiosperm innovation ensures rapid and economical formation of nutritive tissue only when fertilisation is successful (Raven et al., 2013; Mauseth, 2016).

3.4 Homo- and heterophasic reproduction in the context of the life cycle

As noted in the previous section, the concepts of homophasic and heterophasic reproduction help unite all three modes of reproduction into a single system.

Heterophasic reproduction – this is sexual reproduction proper, with obligatory alternation of gametophyte and sporophyte. It is present in all higher plants and forms the basis of their life cycle. It is heterophasic reproduction that generates genetic diversity.
Homophasic reproduction – cloning (vegetative reproduction or reproduction by mitospores). It does not involve alternation of generations and can occur in either phase: a gametophyte can give rise to new gametophytes (e.g., spreading of a fern prothallus), and a sporophyte can give rise to new sporophytes (e.g., rooting of cuttings, formation of bulbs, tubers).

Many plants combine both modes. For example, strawberries reproduce both by seeds (heterophasic) and by runners (homophasic). This gives them an evolutionary advantage: in stable conditions, cloning is efficient; in changing conditions, seeds produce new genotypes capable of adaptation (Barrett, 2017; Serebryakova et al., 2006).

3.5 Biological significance of alternation of generations

The alternation of diploid and haploid generations has deep biological meaning.

The diploid sporophyte gains an advantage through genetic buffering. In a diploid set, harmful recessive mutations may not be expressed because they are masked by dominant alleles. Moreover, accumulation of beneficial mutations in the diploid genome proceeds faster. This promotes increased body size, structural complexity, and longevity of plants (Graham et al., 2014).
The haploid gametophyte serves as a "testing ground" for natural selection. Each gene is present in a single copy and is immediately expressed in the phenotype. This allows efficient elimination of harmful mutations and fixation of beneficial ones at early developmental stages. In seed plants, the gametophyte is extremely reduced and protected by the sporophyte, which reduces risk but retains the possibility of genetic recombination (Evert, 2013; Raven et al., 2013).

Thus, plant life cycles reflect a long evolution from aquatic forms to dominance on land. Understanding the alternation of sporophyte and gametophyte is absolutely necessary for studying such key processes as sporogenesis, pollination, fertilisation, and seed formation, which will be covered in the following sections.

4. Factors and conditions for reproduction

Successful plant reproduction depends on a complex set of external and internal conditions. Even when flowers are formed and ovules are mature, fertilisation and seed development may fail if necessary environmental factors are absent or if the plant experiences resource deficit. In this section, we consider the main groups of factors determining reproductive efficiency – from climatic conditions to biotic interactions and internal resource constraints.

4.1 Abiotic factors

Abiotic (non-living) factors play a decisive role at all stages of the reproductive process: from the formation of reproductive organs to seed germination.

Temperature

Temperature affects flowering time, pollen viability, pollen tube growth rate, and embryo development. Many plants require a period of low temperature (vernalisation) to initiate flowering. Optimal temperatures for pollen germination and tube growth vary among species: for example, in tomato and cucumber they are about 20–30 °C, whereas in some meadow grasses germination can occur at 10–15 °C. Critically high or low temperatures during flowering can cause pollen sterility, disrupt embryo sac development, and lead to complete seed crop failure (Andreeva & Rodman, 2002; Raven et al., 2013).

Water

Water is required for all physiological processes, and for plants with motile sperm (mosses, ferns, some gymnosperms) it is the direct medium for fertilisation. Even in angiosperms, where fertilisation does not require free water, water deficit leads to flower wilting, reduced nectar secretion, poor pollen adhesion to the stigma, and slowed pollen tube growth. Optimal air humidity (60–80%) generally promotes successful pollination and fertilisation, whereas drought or, conversely, prolonged rains can reduce the effectiveness of insect pollinators (Mauseth, 2016; Graham et al., 2014).

Light

Light regulates flowering time (photoperiodism), flower opening, pigment synthesis, and flower attractiveness to pollinators. Many plants flower only at a specific day length (short-day plants – millet, soybean; long-day plants – spinach, radish). Light also affects pollen viability: in some species, pollen formed under insufficient light has reduced fertility. After fertilisation, light is necessary for normal fruit development and seed ripening (Evert, 2013; Simpson, 2019).

4.2 Biotic factors

Biotic factors are the influences of other living organisms on plant reproduction. They can be positive (pollinators, seed dispersers) or negative (parasites, pathogens, competitors).

Pollinators

The vast majority of angiosperms (about 80–90% of species) require the involvement of animal pollinators. These can be insects (bees, bumblebees, butterflies, flies, beetles), birds (hummingbirds, sunbirds), and even bats (in the tropics). The success of cross-pollination directly depends on the abundance, diversity, and activity of pollinators. The decline of pollinator populations due to human impact (pesticide use, habitat destruction) has become one of the major challenges for modern agriculture and conservation biology (Barrett, 2017; Simpson, 2019).

Pathogens and phytophages

Diseases (fungal, bacterial, viral) and pests (insects, mites, nematodes) can directly damage flowers, anthers, ovules, and developing fruits. For example, some fungi (species of Fusarium, Alternaria) cause ovary rot, while caterpillars of the meadow moth can completely destroy inflorescences. In response, plants have evolved defence mechanisms, but at high pathogen abundance, reproductive success can drop to zero (Raven et al., 2013).

Competition for pollinators

In communities where many species flower simultaneously, competition for pollinators arises. Less attractive species (with smaller rewards or less conspicuous flowers) may receive fewer visits and suffer from insufficient cross‑pollination. Evolutionary responses include staggered flowering times, formation of specific relationships with certain pollinator groups, and development of unique signals (flower shape, colour, scent) (Simpson, 2019).

Symbionts (mycorrhiza, bacteria)

Although root symbionts (mycorrhizal fungi, nitrogen‑fixing bacteria) do not directly participate in pollination, they significantly improve the overall physiological condition of the plant, providing it with additional nutrients and water. Plants well supplied with mineral nutrition produce more flowers, more viable pollen, and set more seeds. Thus, the presence of symbionts is an important indirect condition for successful reproduction (Serebryakova et al., 2006; Mauseth, 2016).

4.3 Resources and their allocation

Even under favourable external conditions, reproduction is limited by the plant’s available resources: water, carbohydrates, nitrogen, phosphorus, trace elements. Reproduction is an energy‑intensive process. The formation of flowers, nectar, pollen, and subsequently fruits and seeds requires significant assimilate costs. Many species exhibit so‑called resource limitation: if a plant experiences stress (drought, shading, leaf damage), it may reduce the number of flowers, decrease seeds per fruit, or even abort already set fruits (Barrett, 2017; Graham et al., 2014).

Sexual dimorphism in resource allocation plays an important role: female individuals (in dioecious populations) often spend more resources on fruit and seed production than males do on pollen production. Therefore, in dioecious species, the sex ratio may shift towards males under worsening environmental conditions (Evert, 2013).

4.4 Genetic and demographic factors

Reproductive success is also influenced by internal genetic mechanisms and the spatial structure of populations.

Self‑incompatibility systems: many flowering plants have a genetically programmed inability to self‑pollinate (gametophytic or sporophytic self‑incompatibility). This promotes cross‑pollination, but at low population density or absence of compatible partners, it can lead to complete seed failure (Barrett, 2017; Simpson, 2019). Self‑incompatibility is discussed in more detail in Section 7 "Managing the process".
Population size and isolation: in small, isolated populations, the probability of encountering a pollinator and of cross‑pollination is reduced. The risk of inbreeding depression (reduced fitness due to consanguineous mating) increases. In plants unable to reproduce vegetatively or self‑pollinate, such populations may rapidly go extinct.

4.5 Adaptive strategies under unfavourable conditions

In response to unfavourable external conditions, plants have evolved a number of adaptive strategies to ensure at least minimal reproduction (Serebryakova et al., 2006; Andreeva & Rodman, 2002):

Switch to self‑pollination (autogamy) when pollinators are absent (cleistogamous flowers in violets, touch‑me‑not).
Formation of storage organs and vegetative spreading – when seed reproduction is impossible, the plant may expand its clonal colony (couch grass, ground elder, fireweed).
Production of "insurance" seeds – forming more seeds than can be matured, so that some are lost but the remainder receive sufficient resources.
Synchronisation of flowering within the population (mass flowering) to attract more pollinators and satiate seed consumers.

Thus, a plant’s reproductive success is the sum of many factors – abiotic, biotic, and resource‑related. In the next section, we consider how humans can manage these factors in agronomic practice to improve yield and quality of seeds and fruits.

5. Managing reproduction in agronomy

Humans have interfered with plant reproduction since ancient times to increase yield, improve fruit and seed quality, and preserve valuable cultivars. Modern agronomy has a wide range of techniques – from traditional selection of pollinator varieties to biotechnological methods (micropropagation, genome editing). In this section, we will discuss the main ways to manage the reproductive process in agricultural and ornamental crops.

5.1 Managing pollination and fertilisation

Selection of pollinator varieties

Many fruit and seed crops are self‑sterile or partially self‑sterile: for fruit set they require pollen from another variety or even another species. Classic examples are apple, pear, cherry, plum, as well as most blueberry and kiwifruit cultivars. The agronomic practice is to plant in the same orchard or field at least two inter‑compatible varieties (e.g., with coinciding flowering periods and compatible S‑genes). The distance between varieties must allow effective pollen transfer by wind or insects (usually no more than 30–50 m). Without a suitable pollinator, even with abundant flowering, the yield will be near zero (Chabert and Mallinger, 2025; Mauseth, 2016).

In crops with gametophytic self‑incompatibility (Rosaceae, Solanaceae, Fabaceae), it is important to note that not any two varieties are compatible: they must differ in S‑locus alleles. Nurseries and breeding stations usually publish lists of recommended pollinators for regionalised varieties.

Artificial pollination

When natural pollinators (bees, bumblebees) are insufficient, or when crops are grown under protected cultivation (greenhouses, tunnels), manual or mechanical pollination is applied. For example, in greenhouse tomatoes, vibrating devices (electric "bumblebees") are used to shake flowers, promoting pollen release. In date palms and some pear orchards, pollen collection from male flowers and its application to stigmas of female flowers with brushes or sprayers is practised (Chabert and Mallinger, 2025; Simpson, 2019).

Large horticultural enterprises increasingly resort to commercial pollination using rented honeybee or bumblebee hives. To improve bee efficiency, they are fed sugar syrup scented with the flowers of the target crop. It is important to remember that insecticide use during flowering is strictly prohibited.

Use of growth regulators

To overcome self‑incompatibility or to stimulate fruit set under adverse weather conditions, phytohormones and synthetic growth regulators are applied. For example, treating ovaries with gibberellins (GA₃) induces parthenocarpy (fruit formation without fertilisation) in pear, grape, citrus, and tomato. Parthenocarpic fruits are seedless, which is a commercial advantage for some crops (seedless grape, watermelon, cucumber) (Evert, 2013; Mauseth, 2016).

To stimulate seed set under poor pollination conditions, treatments with auxins or cytokinins are sometimes used; these promote nutrient flow to the ovary and reduce the risk of abortion.

5.2 Managing sex and the reproductive system

Induction of male sterility

In breeding and seed production, genetic male sterility (CMS – cytoplasmic male sterility) is widely used to produce heterotic hybrids without labour‑intensive flower emasculation. In maize, sunflower, sorghum, onion, and carrot, lines with cytoplasmic male sterility have been created; they do not produce viable pollen. Crossing such lines with fertile restorers yields hybrid seeds with high yield (F₁ hybrids). Similarly, in tomato and pepper breeding, nuclear male sterility controlled by recessive genes is used (Chabert and Mallinger, 2025; Andreeva & Rodman, 2002).

Sex control in dioecious crops

In dioecious plants (e.g., sea buckthorn, kiwifruit, spinach, hemp), both female and male individuals must be planted to obtain fruits. The ratio is usually 1 male plant to 5–10 females. Methods for early sex determination using DNA markers have been developed, allowing culling of "extra" male plants when establishing plantations (Simpson, 2019).

5.3 Vegetative propagation as a management tool

To preserve cultivar traits (which segregate during seed propagation), vegetative propagation is used:

Cuttings – rooting of stem, leaf, or root segments. Used for grapes, currants, roses, chrysanthemums, and many houseplants. Treating cuttings with auxins (indolebutyric acid, heteroauxin) stimulates adventitious root formation (Mauseth, 2016).
Grafting – joining a scion (cultivar part) with a rootstock (a plant with a strong root system, often a seedling or clone). Used in fruit growing (apple, pear, cherry, citrus) and ornamental horticulture (roses, rhododendrons). Grafting allows combining high fruit quality with winter hardiness, drought tolerance, or dwarfing properties of the rootstock (Evert, 2013).
Propagation by tubers, bulbs, rhizomes – traditional method for potatoes, tulips, gladioli, irises, asparagus. To speed up propagation, tubers and bulbs are cut into pieces (each with a bud or basal plate).

5.4 Micropropagation (tissue culture)

Micropropagation (clonal micropropagation) is an in vitro vegetative propagation method that allows obtaining hundreds of thousands of genetically identical plants (clones) from a single explant (apical bud, leaf fragment, meristem). Main steps (Serebryakova et al., 2006; Andreeva & Rodman, 2002):

Establishment – sterilisation of the explant and planting on a nutrient medium.
Multiplication – induction of multiple shoot formation using cytokinins (benzyladenine, kinetin).
Rooting – transfer of shoots to a medium with auxins to induce rhizogenesis.
Acclimatisation – gradual hardening of regenerant plants to greenhouse conditions (reducing humidity, increasing light).

Advantages: production of virus‑ and bacteria‑free plants (via meristem culture), rapid reproduction of valuable and rare genotypes, ability to propagate species with difficult‑to‑germinate seeds or poor cutting ability. Micropropagation is widely used for potatoes, strawberries, orchids, anthurium, chrysanthemums, as well as for conservation of rare and endangered species (Mauseth, 2016).

5.5 Managing seed productivity

To obtain high‑quality seeds, the following agronomic practices are used:

Optimising mineral nutrition – ensuring plants receive phosphorus and potassium (especially during budding and flowering), because excess nitrogen stimulates vegetative growth at the expense of reproductive growth.
Regulating sowing density – too dense sowing leads to shading, reduced flower numbers, and lower seed set. For seed production, lower seeding rates are recommended.
Micronutrient application – boron, zinc, molybdenum, manganese are essential for normal pollen development and fertilisation. Foliar boron sprays (boric acid) are often applied to seed crops of clover, alfalfa, sugar beet, and sunflower.
Hybridisation using male sterility systems – as mentioned, allows mechanised production of hybrid seeds (maize, rice, sorghum, sunflower, onion, carrot) (Chabert and Mallinger, 2025).

5.6 Managing fruit quality through xenia

The phenomenon of xenia – the direct influence of pollen on seed and fruit properties not related to egg fertilisation (Denney, 1992; Liu, 2018). In maize, for example, paternal pollen determines the colour and shape of the kernel (endosperm is triploid, carrying two maternal sets and one paternal set). In fruit crops (apple, pear, persimmon), pollen can affect fruit weight, ripening time, sugar content, and even storage life. In agronomic practice, this is taken into account when selecting pollinator varieties: for instance, for apple cultivar 'Golden Delicious', the best pollinator is 'Red Idared', and for 'Fuji' – 'Gala'. By applying pollen from different donors, fruits with different commercial qualities are obtained (Chabert and Mallinger, 2025).

5.7 Ethical and environmental aspects

When using reproductive management methods (especially genetic engineering and micropropagation), precautions must be taken:

Prevent the escape of transgenic forms into natural populations (isolation, pollen control).
Maintain genetic diversity of cultivars, not replacing all local populations with uniform clones.
Avoid excessive use of chemical regulators that may accumulate in products.

6. Significance for agriculture and biotechnology

The study of plant reproduction has not only fundamental but also immense applied importance. Understanding the mechanisms of pollination, fertilisation, seed and fruit formation, and vegetative cloning underlies modern seed production, breeding, pomology, and biotechnology. In this section, we consider key applications of knowledge about plant reproduction in the agrifood sector and related fields.

6.1 Seed production and hybrid seed production

The main task of seed production is to supply agriculture with high‑quality seeds while preserving cultivar traits. For self‑pollinating crops (wheat, barley, rice, pea, tomato, pepper), seed production is carried out by individual or mass selection with spatial isolation of varieties to avoid accidental cross‑pollination. For cross‑pollinated crops (maize, rye, sunflower, buckwheat, many vegetables of the Cucurbitaceae and Brassicaceae families), cross‑pollination between related lines must be ensured while preventing contamination by pollen from other varieties. This is achieved by spatial isolation (at least 200–1000 m) or temporal isolation (staggered flowering times) (Andreeva & Rodman, 2002; Mauseth, 2016).

F₁ hybrid seed production is based on heterosis (hybrid vigour), where the progeny from crossing two inbred lines outperforms the parents in yield, earliness, disease resistance. To produce hybrid seeds, the maternal (sterile or emasculated) line must be artificially crossed with the paternal (fertile) line. The most economical method is the use of cytoplasmic male sterility (CMS), which is maternally inherited. CMS is widely used in seed production of maize, sorghum, sunflower, onion, carrot, sugar beet. To restore fertility in hybrid progeny, restorer lines (Rf genes) are used (Chabert and Mallinger, 2025; Evert, 2013).

In recent decades, genetically engineered male sterility systems have also been used for hybrid seed production (e.g., the barnase/barstar system in rapeseed, maize, rice). These systems allow fully sterile maternal lines without traditional flower emasculation.

6.2 Variety testing and pollinator selection in horticulture

For fruit, berry, and nut crops, proper selection of pollinator varieties is a prerequisite for stable yields. As noted in Section 5, many apple, pear, cherry, plum, sweet cherry, myrobalan plum, honeysuckle, blueberry, kiwifruit, and hazelnut cultivars are self‑sterile or partially self‑sterile. Nurseries and horticultural enterprises produce compatibility tables indicating the best pollinators by flowering time and genetic compatibility. For example, for apple, the cultivar 'Antonovka' is well pollinated by 'Anise Striped', 'Moscow Pear', 'Cinnamon Striped', but poorly by 'Pepin Saffron' and 'Welsey' (Chabert and Mallinger, 2025).

When establishing commercial orchards, it is recommended to plant at least 3–4 cultivars, alternating them in rows or groups, and to keep distances between cultivars no more than 30–50 m for effective bee‑mediated pollen transfer. In amateur gardening, one pollinator per 5–10 trees of the main cultivar may suffice (Simpson, 2019).

6.3 Conservation and propagation of rare and endangered species

Knowledge of plant reproduction is critically important for biodiversity conservation. For many rare, threatened species, natural seed reproduction is hindered by low population numbers, absence of pollinators, or disturbed habitats. In such cases, the following are applied:

Artificial pollination with hand‑transfer of pollen between individuals.
Micropropagation (tissue culture) to obtain large numbers of genetically identical plants, which are then reintroduced into the wild. This method has been successfully used for orchids, cycads, some endemic palms and succulents (Mauseth, 2016; Serebryakova et al., 2006).
Seed banks (cryobanks), where seeds are stored at low temperatures and controlled humidity. For many species, pre‑treatment with stratification, scarification, or growth regulators is needed to break dormancy. Understanding germination physiology allows the development of protocols for population restoration from stored seeds.

6.4 Biotechnological methods for plant improvement

Modern biotechnology offers methods to control the reproductive process at the cellular and molecular level.

Somatic hybridisation (protoplast fusion)

To overcome cross‑incompatibility between species (especially in Solanaceae, Brassicaceae, Apiaceae), fusion of isolated protoplasts (cells without cell walls) using an electric field or polyethylene glycol is used. The resulting somatic hybrids can combine genomes of distant species that do not cross normally. In this way, hybrids of potato and tomato, rapeseed and radish, and citrus have been created (Evert, 2013). The main problem is that chromosomes from one parent are often lost, but in some cases fertile allopolyploids have been obtained.

Genetic engineering (transgenic plants)

Genetic engineering methods allow the insertion of individual genes into the target plant genome, including those affecting reproductive traits. The most significant directions for agriculture (Chabert and Mallinger, 2025; Andreeva & Rodman, 2002):

Overcoming or inducing self‑incompatibility – introduction of S‑RNase or SLF genes to create self‑fertile lines from self‑incompatible ones (e.g., in tomatoes, eggplants, some cherry cultivars).
Genetic male sterility – expression of a cytotoxic gene (barnase) under a tapetum‑specific promoter in anthers. Such lines are used to produce hybrid seeds without emasculation (rapeseed, maize, rice, soybean).
Parthenocarpy – introduction of a gene causing fruit set without fertilisation (e.g., the iaaM gene under an ovary‑specific promoter). This yields seedless fruits (tomatoes, cucumbers, eggplants, watermelons) with improved market qualities.
Increased fruit and seed size – regulation of genes responsible for cell expansion and storage accumulation (genes from the CNR, KLUH, ARF families, etc.) (Mauseth, 2016).

Genome editing (CRISPR/Cas)

The CRISPR/Cas system allows targeted changes to specific DNA regions without introducing foreign genes. It has already been used to obtain:

Self‑fertile lines of kiwifruit and citrus (knockout of S‑RNase or SLF genes).
Plants with altered flowering time (knockout of flowering repressor genes).
Crops with improved seed set under unfavourable temperatures (modifying genes involved in pollen development).

Genome editing is considered less regulated than creating transgenic plants (GMOs) because no foreign sequences are introduced into the final product.

6.5 Economic importance and food security

Agriculture directly depends on successful reproduction of crop plants. According to FAO estimates, more than 75% of major food crops (including fruits, vegetables, nuts, oilseeds, and legumes) require animal pollination. The economic value of insect pollination is estimated at hundreds of billions of dollars per year. The decline of wild pollinator populations and honeybee colony collapse (colony collapse disorder) pose serious risks to global food security (Barrett, 2017; Chabert and Mallinger, 2025).

In response, targeted pollinator management strategies are being developed: placement of hives, creation of entomological reserves, reduction of insecticide use during flowering, sowing nectar‑producing companion plants to support wild bee and bumblebee populations.

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