Fruit

The primary function of the fruit is to protect developing seeds from adverse environmental factors. This function is realised both during seed formation inside the ovary and after seed maturation. The pericarp (fruit wall) creates a mechanical barrier that prevents seed damage by animals as well as the impact of sharp temperature and humidity fluctuations (Yakovlev et al., 2008).

Especially important is sealing: the closed ovary of the pistil forms a moist chamber that protects ovules from desiccation. Thanks to this, angiosperms were able to colonise arid territories where dependence on liquid water is critical (Yakovlev et al., 2008). Moreover, many fruits contain alkaloids, tannins, and other compounds in their pericarp tissues that deter or are toxic to herbivores, also contributing to seed protection (Bobrov & Romanov, 2019; Ahn et al., 2025).

The second most important biological function of the fruit is to ensure the spread of seeds (diaspores) to new territories. This reduces competition between the mother plant and its offspring and promotes colonisation of new habitats. The evolution of fruits has led to the formation of diverse adaptations for dispersal by various agents — wind, water, animals, as well as active self‑dispersal (Ballester & Ferrándiz, 2017; Ahn et al., 2025).

Depending on the dispersal mode, several main types are distinguished (Stern, 2021; Simpson, 2017):

The development of particular dispersal adaptations is the result of long‑term co‑evolution of plants with animals and abiotic environmental factors (Ahn et al., 2025; Ballester & Ferrándiz, 2017).

During fruit development, reserve substances — carbohydrates, proteins, lipids, vitamins — accumulate in its tissues (pericarp) and in the seeds. These reserves are used either by the fruit itself during ripening or directly by the seedling after seed germination. This is especially pronounced in fleshy fruits, where the pulp (mesocarp) contains significant amounts of sugars, organic acids, pectins, as well as aromatic substances that attract dispersers (Yakovlev et al., 2008; Stern, 2021).

Furthermore, developing seeds secrete hormones (auxins, gibberellins) that stimulate pericarp growth. Without fertilisation and seed formation, the fruit usually does not develop (although parthenocarpy — fruit formation without seeds — also exists). Thus, the fruit acts as a hormonally active structure coordinating the development of the entire flower after fertilisation (Stern, 2021; Bu et al., 2025).

For humans, fruits and seeds of flowering plants have enormous economic significance. They serve as a source of food, industrial raw materials, animal feed, and medicinal substances (Yakovlev et al., 2008; Stern, 2021).

From an agronomic point of view, the fruit is the yield organ. The main groups of agricultural crops that utilise fruits or seeds include:

Fruit quality — size, shape, colour, firmness, chemical composition — is the subject of breeding programmes and agronomic practices. Modern research is aimed at identifying genetic and hormonal mechanisms controlling fruit size and shape, resistance to cracking, shelf life, and transportability (Bu et al., 2025; Zhao et al., 2024).

Thus, the fruit not only fulfils the biological mission of protecting and dispersing seeds, but also serves as a key object of agricultural production, determining food security and economic well‑being of humanity.

The main mass of the fruit is the pericarp (from Greek peri — around, karpos — fruit), which develops from the ovary walls and, sometimes, from other parts of the flower (receptacle, hypanthium, calyx). The pericarp surrounds the seeds and performs protective and dispersal functions (Yakovlev et al., 2008; Bobrov & Romanov, 2019).

Typically, three layers are distinguished in the pericarp, which may be expressed to varying degrees (Cerri & Reale, 2020; Evert, 2006):

Depending on the fruit type, these three layers may be clearly distinguishable or, on the contrary, weakly differentiated. For example, in berries (tomato, grape) all layers are fleshy and do not separate into distinct zones, while in dry fruits (legume, capsule) they are usually dry and often fused together (Simpson, 2017; Bobrov & Romanov, 2019).

The entire diversity of angiosperm fruits is divided into several major groups. The most fundamental division is based on pericarp consistency: fleshy and dry fruits (Cerri & Reale, 2020; Stern, 2021). Within these groups several subtypes are distinguished.

In addition to the simple fruits described above (developing from a single pistil), there are fruits formed by several pistils of one flower (aggregate, or apocarpous) and fruits formed from a whole inflorescence (multiple fruits) (Simpson, 2017; Bobrov & Romanov, 2019).

The morphological diversity of fruits serves as a reliable systematic feature for plant identification and reflects their evolutionary adaptations to dispersal modes (Ahn et al., 2025; Simpson, 2017).

The main criteria used in fruit classification (according to Yakovlev et al., 2008; Bobrov & Romanov, 2019):

This classification is considered the most natural because it reflects evolutionary transformations.

This classification is convenient for plant identification and is often used in field guides (Stern, 2021; Evert, 2006).

I. Fleshy fruits (pericarp fleshy, juicy)

II. Dry fruits

A. Dehiscent (seeds shed)

B. Indehiscent (seeds remain inside the fruit)

A more detailed classification based on the anatomical structure of the pericarp and the arrangement of sclerenchymatous (mechanical) layers was proposed by Bobrov & Romanov (2019). They distinguish 27 morphogenetic types grouped into 8 main categories: follicle, achene, drupe, berry, capsule, pyrenarium, amphisarca, nut. This classification accounts for tissue homology and allows understanding of evolutionary transitions between fruit types. For example, based on the localisation of sclerenchyma in the pericarp, four types of follicles are distinguished (Hakea‑, Illicium‑, Myristica‑, and Talauma‑types), etc. (Bobrov & Romanov, 2019).

Comparative analysis of classifications reveals the following trends in fruit evolution (Ahn et al., 2025; Bobrov & Romanov, 2019):

Thus, fruit classification not only serves diagnostic purposes but also reveals the paths of adaptive evolution of angiosperms related to the efficiency of seed protection and dispersal (Ballester & Ferrándiz, 2017; Ahn et al., 2025).

As noted earlier, the pericarp develops from the ovary wall. In ontogeny three histogenetic zones can be distinguished, corresponding to the three layers of the ovary (Bobrov & Romanov, 2019; Roland & Roland, 1980):

In the mature fruit these zones may be clearly distinguishable or may merge. Moreover, in fruits developing from an inferior ovary, the outer layer of the pericarp may be supplemented by tissues of the hypanthium or receptacle; such an outer layer is called epicarp (not to be confused with exocarp!) (Bobrov & Romanov, 2019).

The protective function in fruits is performed mainly by the exocarp (or epicarp). The outer epidermis of the fruit is usually covered with a cuticle, often quite thick and waxy (Evert, 2006). In some fruits the exocarp contains stomata (e.g., in apples, plums), which may be functional or die off during ripening. In many dry fruits (legumes, capsules) the exocarp is a single‑layered epidermis with thickened, sometimes lignified, cell walls (Cerri & Reale, 2020).

Specialised structures of the exocarp:

In fleshy fruits with delicate skin (tomato, grape) the exocarp is thin, without mechanical thickenings, which facilitates its easy damage when eaten by animals (endozoochory).

Mechanical tissues provide strength to the pericarp, protect seeds, and, in dehiscent fruits, participate in the disruption of the fruit wall. They are represented mainly by sclerenchyma (fibres and sclereids) and collenchyma.

In dry dehiscent fruits, mechanical tissues are arranged such that upon drying they create stresses leading to pericarp rupture along dehiscence lines (Ballester & Ferrándiz, 2017).

Vascular bundles (phloem and xylem) run through the pericarp; they are continuations of the bundles of the pedicel and receptacle. They supply the developing fruit with water, minerals, and organic compounds (Evert, 2006).

In the mature fruit, vascular elements are often reduced: sieve tubes collapse, and xylem vessels may become filled with air or tyloses. Nevertheless, vascular bundles are visible in fruits as veins or a network (e.g., in apple skin, in capsule septa, in legume valves). The arrangement of bundles helps define the boundaries between exocarp, mesocarp, and endocarp (Cerri & Reale, 2020).

The bulk of the mesocarp (and sometimes other layers) is composed of parenchyma. In fleshy fruits, parenchyma cells contain large vacuoles with juice rich in sugars, organic acids, flavonoids, and vitamins. Intercellular spaces are often well developed (e.g., in apple, watermelon). Parenchyma cells may be storage cells (starch, fatty oils, proteins) (Evert, 2006; Cerri & Reale, 2020).

In dry fruits, the parenchyma often degenerates before maturity, turning into thin films. In some dry fruits (Apiaceae — mesocarp parenchymatous with essential oil ducts).

A variant of parenchyma is aerenchyma — tissue with highly developed intercellular spaces containing air. It is characteristic of fruits of hydrophytes (Nuphar, Nymphaea), providing buoyancy.

Specialised secretory structures — cavities, canals, glandular hairs — are often found in the pericarp. They may produce essential oils (in citrus — glands in the exocarp), resins, mucilage, as well as pheromones and repellents (Evert, 2006).

The cell walls of the pericarp can be complex in composition: in addition to cellulose, they contain lignin (provides rigidity), cutin, suberin (in dermal tissues), pectic substances (in fleshy fruits — they soften during ripening due to pectin degradation). The presence of pit fields and plasmodesmata in living parenchyma and endosperm cells allows short‑distance transport (Evert, 2006).

Thus, the anatomy of the pericarp is a complex set of tissues structurally and functionally adapted to protect seeds, nourish them, and ensure effective dispersal. Understanding the tissue composition of fruits is necessary for breeding, yield quality assessment, as well as for phylogenetic reconstructions and plant evolutionary biology (Ahn et al., 2025; Bobrov & Romanov, 2019).

Fruit initiation begins after pollination and fertilisation, although in some plants parthenocarpic fruits may develop without fertilisation (banana, orange, cucumber) (Stern, 2021). Fertilisation triggers a cascade of signalling events, the key among which are hormonal changes:

If fertilisation does not occur, the ovary usually withers and abscises. However, in many cultivated plants (tomato, cucumber, citrus) varieties capable of parthenocarpy have been bred, allowing seedless fruits to be obtained, which consumers appreciate (Stern, 2021).

After initiation, active fruit growth begins. Growth consists of two components: cell division (mitosis) and cell expansion (increase in cell size due to water uptake and synthesis of cytoplasm and cell wall). The ratio of these processes depends on the fruit type and its age (Bu et al., 2025).

The rate and duration of fruit growth are often described by an S‑shaped curve (one rapid growth phase) or a double S‑shaped curve (in drupes: two rapid growth phases separated by a pause — the period of stone hardening) (Stern, 2021; Bu et al., 2025).

Concurrently with growth, differentiation of pericarp tissues occurs. Cells formed by divisions become specialised:

The differentiation process of pericarp tissues in different fruit types is detailed in the work of Bobrov & Romanov (2019), where 27 morphogenetic types are distinguished based on anatomy.

Ripening is a set of physiological and biochemical changes that make the fruit soft, develop characteristic colour, aroma, and taste, making it attractive to dispersers (for fleshy fruits) or, conversely, dry and light (for dry fruits). This process is regulated by the hormone ethylene (in climacteric fruits) and other factors (Ahn et al., 2025; Bu et al., 2025).

Main changes during ripening:

In dry fruits, ripening is accompanied by tissue dehydration, lignification, and often the formation of dehiscence lines. In some dry fruits (legumes, capsules), the stress created by drying causes explosive dehiscence (Ballester & Ferrándiz, 2017).

After reaching full maturity, the fruit may remain on the plant for some time, but eventually senescence sets in. It is accompanied by further degradation of cell walls, destruction of organelles, and water loss. In fleshy fruits, senescence leads to over‑ripening — softening, spoilage, rotting. In dry fruits, senescence is expressed in valve rupture (dehiscence) and seed shedding, or in gradual breakdown of the pericarp by microorganisms and weather (Bobrov & Romanov, 2019).

Hormonal regulation of senescence includes activation of senescence‑associated genes, synthesis of ethylene and abscisic acid, and suppression of cytokinin and gibberellin synthesis (Bu et al., 2025).

Fruit formation and development are strongly influenced by environmental factors and agronomic practices (Yadav et al., 2023; Bu et al., 2025):

Parthenocarpy (from Greek parthenos — virgin, karpos — fruit) — fruit formation without fertilisation (not to be confused with apomixis — seed formation without fertilisation). Parthenocarpic fruits contain no seeds. They occur naturally in some species (banana, pineapple, fig) and can also be induced by treating ovaries with auxins or gibberellins (Stern, 2021). In agriculture, seedless grape, watermelon, cucumber, and citrus varieties are highly valued.

Apomixis (seed formation without fertilisation) can also be accompanied by fruit development, but seeds then arise from an unfertilised egg cell or a somatic cell of the ovule (Yakovlev et al., 2008).

It is important to emphasise that fruit development is closely linked to seed development. Hormones produced by seeds (especially auxin) stimulate pericarp growth. If seeds do not develop, the fruit often lags in growth or abscises. In multi‑seeded fruits (apple, pumpkin, tomato), the distribution and number of seeds affect fruit shape and size — this phenomenon is called xenia (pollen influence on fruit and seed properties) (Chabert & Mallinger, 2025). For example, pollination with a mixture of pollen from different varieties can increase fruit mass and sugar content.

Thus, fruit ontogeny is a synchronised process of cell divisions, expansion, tissue differentiation, and biochemical transformations, regulated by hormones, genes, and environmental factors. Understanding these processes is essential for managing fruit production in agriculture and for breeding new varieties with desired fruit qualities (Bu et al., 2025; Zhao et al., 2024).

Temperature regime is one of the key factors determining the success of fruit set and development.

Water participates in maintaining cell turgor, transporting nutrients, and regulating tissue temperature through transpiration.

Light affects fruiting both through photosynthesis (providing assimilates) and through photoreceptor mechanisms (phytochromes, cryptochromes).

Adequate and balanced nutrition is necessary for normal fruit formation. Deficiency or excess of elements causes disorders:

Agronomic practice includes nutritional diagnosis (leaf analysis, soil testing) and fertiliser application at critical stages (flowering, fruit set, filling) to obtain high‑quality yields.

Some environmental factors can induce parthenocarpy (fruit formation without seeds) — for example, severe heat or drought during flowering sometimes suppresses pollination, but the ovary then begins to develop parthenocarpically (in eggplant, pepper). This can lead to the formation of seedless, misshapen fruits of no commercial value (Stern, 2021).

Fruit cracking (physiological disorder) is caused by sharp fluctuations in water supply (alternating drought and heavy rain), high temperatures, and calcium deficiency. It is especially characteristic of cherry, plum, tomatoes, watermelons, and carrots (a root vegetable, but the mechanism is similar). Cracking opens the way for infections and sharply reduces shelf life.

Empty grains (formation of fruits with underdeveloped or no seeds) result from impaired fertilisation due to low temperatures, drought, wind, lack of pollinators, or pesticide stress. In cereals, empty grains (shrivelled grains) sharply reduce yield. In fruit crops (apple, pear), empty grains manifest as small, underdeveloped fruits that often fall off before ripening (Yadav et al., 2023).

Fruit formation is impossible without successful pollination and fertilisation. A lack of insect pollinators (bees, bumblebees, flies, beetles) due to adverse weather or insecticide use leads to reduced fruit set, especially in entomophilous crops (apple, pear, raspberry, sunflower, cucurbits) (Chabert & Mallinger, 2025). In protected cultivation, bumblebees or artificial vibration are used to pollinate tomatoes and peppers.

Pests (fruit moths, weevils, gall midges) damage ovaries and young fruits, causing abscission or deformation. Diseases (grey mould, anthracnose, late blight, powdery mildew) infect fruits at various stages, impairing quality and causing premature spoilage (Yadav et al., 2023). Integrated pest management (IPM) includes a set of measures to minimise damage without harming pollinators.

In response to unfavourable conditions, plants activate defence mechanisms: synthesis of antioxidants, heat shock proteins, osmoregulators (proline, sucrose). Breeding for stress tolerance (heat resistance, drought tolerance, cracking resistance) is an important task of modern plant science (Bu et al., 2025).

Agronomic practices can mitigate environmental impacts:

Thus, managing environmental factors together with the genetic potential of the variety allows stable yields of high‑quality fruits. A deep understanding of autecological responses of fruits is necessary to adapt agriculture to climate change (Yadav et al., 2023).

In many fruit and vegetable crops, the number of set fruits generally exceeds the plant’s capacity to nourish them. Excessive fruit load leads to small fruits, poor taste, reduced market quality, and can cause biennial bearing (alternation of heavy and light crops). To address this, crop load management — artificial thinning of flowers or young fruits — is applied (Stern, 2021).

Plant growth regulators (phytohormones and their synthetic analogues) allow targeted manipulation of flowering, fruit set, growth, and ripening (Bu et al., 2025; Stern, 2021).

Gibberellins (GA, gibberellic acid) — used for:

Auxins (2,4‑D, NAA, dicamba) — used for:

Cytokinins (kinetin, benzylaminopurine) — less commonly used to increase fruit set and accelerate growth of young fruits (grape, apple). Applied in combination with gibberellins.

Ethylene and ethylene‑releasing compounds (ethephon) — used for:

Abscisic acid (ABA) — not yet widely used in agriculture, but is being studied as a means to accelerate fruit colouring (grape, apple) and increase stress tolerance.

For many fruit and seed crops (apple, pear, cherry, sunflower, rapeseed, cucurbits), insufficient cross‑pollination is a yield‑limiting factor. Agronomic practices include (Chabert & Mallinger, 2025):

Fruit quality is determined by size, weight, colour, sugar content, acids, vitamins, aromatic compounds, as well as resistance to mechanical damage and diseases during storage.

Defoliants — substances that cause premature leaf drop. Used to facilitate harvest (cotton, soybean) and to improve light penetration and fruit colouring (grape, apples). Defoliants accelerate fruit ripening by redirecting assimilates to fruits (Yadav et al., 2023).

Wax coating and polishing — application of a thin layer of food‑grade wax or paraffin to the fruit surface (citrus, apples, cucumbers) allows:

Controlled atmosphere storage (CA storage) — fruits and seeds of many crops are stored at reduced temperature (0–4 °C), reduced oxygen (2–5%), and elevated carbon dioxide (up to 10%). This slows respiration, ripening, and rot development. For apples, pears, tomatoes, grapes, citrus, CA storage is a standard technology that extends market life to 6–12 months (Stern, 2021).

Gas exchange in storage — removal of ethylene (by absorbers or catalytic oxidisers) prevents over‑ripening and spoilage. Carbon dioxide sorbents maintain its concentration within desired limits.

Treatment with antioxidants and fungicides — to suppress post‑harvest diseases (Fusarium, black rot, Penicillium rot), fruits are treated with approved fungicides (imazalil, thiabendazole, propiconazole) before storage.

Apple: chemical (NAA) or mechanical fruit thinning; placement of pollinizer varieties; gibberellin sprays to increase fruit size; defoliants to improve colour; CA storage up to 12 months.

Grape: gibberellin for seedless berries; ethylene to accelerate ripening and leaf drop; wax coating to improve shelf life; fungicide treatments against grey mould.

Tomato (commercial): use of parthenocarpic hybrids for protected cultivation; bumblebee pollination; forced ripening in ethylene chambers after harvest; CA storage at 12–14 °C.

Citrus (orange, lemon): fruit thinning to increase size; wax coating; fungicide treatment (thiabendazole) against green and blue mould; CA storage up to six months.

Cereals (wheat, rice): regulation of stem density; use of retardants to prevent lodging; desiccation to accelerate ripening and facilitate harvest; grain drying to 14% moisture for long‑term storage.

Proper agronomic management of fruiting can increase marketable yield by 20–50% and reduce post‑harvest losses. However, the use of chemical regulators and intensive technologies must be environmentally sound to avoid accumulation of residues in products and environmental pollution. In recent years, integrated fruit management systems have been actively developed, combining biological (entomophages, microbial antagonists) and agrotechnical methods with minimal use of chemicals (Bu et al., 2025; Yadav et al., 2023).

Thus, practical management of fruiting is a multidisciplinary field based on knowledge of fruit morphology, physiology, genetics, and autecology. Its successful application ensures food security and profitability of agricultural production.