Juvenile Stage

Preceding stage — latent (seed). The seed contains a formed embryo that is in a state of enforced or organic dormancy. During this period, metabolic activity is extremely low, and development is suspended until favorable conditions arrive (Raven et al., 2013). The end of the latent stage and the initiation of germination mark the beginning of the juvenile stage.

Subsequent stage — virginile. In the Russian school of age morphology (Gatsuk et al., 1980), the virginile state is defined as the stage at which the plant reaches the typical vegetative structure for the species (e.g., a branched shoot with “adult”-type leaves) but is not yet capable of flowering. The key difference between the juvenile stage and the virginile stage is the absence of the ability for vegetative propagation in juvenile individuals. In most perennial herbs and woody plants, cuttings taken from juvenile shoots do not root or produce weak roots, whereas virginile individuals readily propagate vegetatively (Poethig, 2013).

Seed imbibition and activation of metabolism. Water absorption leads to the rupture of the seed coat, activation of enzymes, and mobilization of reserve substances from the endosperm or cotyledons (Raven et al., 2013).

Resumption of cell division in the embryo meristems. The apical meristems of the root and shoot exit dormancy and begin to actively produce new cells. Already at the early stages of germination, primary tissues are laid down: protoderm, ground meristem, and procambium (Graham et al., 2014).

Emergence of the seedling. Typically, the radicle is the first to emerge from the seed, anchoring the seedling in the substrate and beginning to absorb water and mineral ions. This is followed by the extension of the hypocotyl (in species with epigeal germination) or epicotyl (in species with hypogeal germination), bringing the cotyledons and the first pair of true leaves to the surface (Bidlack & Jansky, 2021).

Transition to autotrophic nutrition. The cotyledons (or the first green leaves) begin to photosynthesize. Gradually, the plant ceases to depend on seed reserves and fully switches to independent carbon nutrition.

juvenile stage / juvenile phase (Poethig, 2013; Manuela & Xu, 2020)

seedling stage (for the seedling phase)

vegetative phase change — transition from the juvenile phase to the adult vegetative phase (Liao & Xu, 2026)

Epigeal germination. Characteristic of beans, maple, pumpkin, sunflower. The hypocotyl actively elongates, bringing the cotyledons above the soil surface. The cotyledons turn green and begin to photosynthesize, acting as the first assimilating organs.

Hypogeal germination. Observed in peas, oak, many grasses. The hypocotyl remains short, while the epicotyl elongates, bringing the true leaves to the surface. The cotyledons remain underground and serve as a reservoir of reserve substances, which are gradually expended on the growth of the seedling.

Storage — in species with hypogeal germination, cotyledons contain starch, proteins, and oils.

Absorptive (haustorial) — in grasses, the cotyledon (scutellum) absorbs nutrients from the endosperm and transfers them to the growing embryo (Serebryakova et al., 2006).

Photosynthetic — in species with epigeal germination, cotyledons become green and assimilate carbon dioxide.

Protective — cotyledons can cover the apical bud in the seedling phase.

Presence of first true leaves (usually 1–3 pairs), which may differ markedly from adult plant leaves in shape, size, pubescence, and degree of dissection. In eudicots (e.g., ivy Hedera helix), juvenile leaves are lobed, while adult leaves are entire; in acacias, juvenile leaves are pinnate, while adult leaves are transformed into phyllodes (Zotz et al., 2011).

Simple shoot structure: the main shoot is generally unbranched or weakly branched (lateral shoots are absent or in a rudimentary state). Growth pattern is monopodial (Serebryakova et al., 2006).

Root system still retains primary structure characteristics: the taproot is well expressed, lateral roots are few, adventitious roots are absent or just beginning to form.

Lack of ability for vegetative propagation. Cuttings taken from juvenile shoots generally do not root or produce weak callus; this is an important diagnostic feature for separating the juvenile phase from the virginile phase (Gatsuk et al., 1980).

Simpler shape. In many woody and herbaceous plants, juvenile leaves are less dissected, entire or shallowly lobed, while adult leaves may be deeply lobed, palmately or pinnately dissected. A classic example is ivy (Hedera helix): juvenile leaves have 3–5 lobes, whereas adult leaves are ovate-rhombic, entire (Zotz et al., 2011).

Smaller size. Juvenile leaves are generally smaller than adult leaves. In English oak (Quercus robur), the first leaves of the seedling are 5–10 times smaller than the leaves of an adult tree.

Different pubescence. Hairs (trichomes) on juvenile leaves may be denser or, conversely, absent. In Arabidopsis thaliana, the abaxial (lower) side of juvenile leaves is glabrous, while adult leaves are covered with trichomes (Manuela & Xu, 2020). In tomato, juvenile leaves have denser pubescence, which is later reduced.

Different coloration. Sometimes juvenile leaves contain more anthocyanin (reddish tint) or, conversely, are lighter due to a smaller number of chloroplasts. However, this trait varies depending on light and is not universal.

Unbranched or weakly branched main shoot. In most woody species (pine, spruce, oak), in the juvenile phase, the main shoot grows monopodially, and first-order lateral shoots are absent or represented by a few short branches (“brachyblasts”). In herbaceous plants (wheat, barley), juvenile plants generally do not tiller or tiller weakly (Serebryakova et al., 2006).

Thinner and more herbaceous stem. In woody plants, juvenile stems do not lignify or only partially lignify. Secondary protective tissues (periderm) are absent, and the stem is covered by epidermis with stomata.

Different phyllotaxis (leaf arrangement). In some species, the order of leaf placement may differ on juvenile and adult shoots. For example, in eucalypt (Eucalyptus globulus), juvenile leaves are opposite, while adult leaves are alternate (Zotz et al., 2011).

Ability to form adventitious roots (rhizogenesis). In juvenile shoots, the ability to root is reduced (see Section 2), which is associated with the absence or weak development of cambium and bast fibers from which root primordia form.

Taproot clearly expressed. In dicotyledons and gymnosperms, the embryonic (tap) root is well developed at the juvenile stage. It grows vertically downward and bears few first-order lateral roots. A taproot system is formed (Serebryakova et al., 2006).

Adventitious roots absent or few. In many grasses, adventitious (nodal) roots begin to form only during the transition to the virginile state — in the tillering phase. In red clover, adventitious roots on the stem appear only after the main shoot has elongated sufficiently.

Thin root tips. The absorption zone of the root is relatively longer than in the adult plant, and the proportion of mechanical tissues in the central cylinder is smaller. The root cap is well developed.

Mycorrhiza. In many woody species (pine, oak, birch), infection of roots by mycorrhizal fungi occurs already at the juvenile stage, which increases the absorptive capacity of the roots. However, full ectomycorrhiza forms only after several years.

Annual herbs (ephemerals). The juvenile stage is extremely short — from 1 to 3–4 weeks after emergence. In radish, garden cress, spring cereals, the transition to the virginile state (formation of adult leaves and beginning of branching) occurs already at the 2–3 true leaf stage. Accelerated development allows annuals to complete their life cycle in one growing season (Raven et al., 2013).

Biennial herbs. In the first year of vegetation, the plant is in the juvenile (and then immature) phase, forming a basal rosette of leaves. Only after overwintering and vernalization does it transition to the virginile and generative stages. Thus, the juvenile stage can last 6–10 months (in carrot, beet, cabbage) (Serebryakova et al., 2006).

Perennial herbs. In meadow grasses (fescue, timothy), the juvenile stage lasts 2–5 weeks, after which tillering (virginile state) begins. In legume grasses (clover, alfalfa), the juvenile phase can be prolonged to 1–2 months. In forest perennial herbs (lily of the valley, wild ginger), the juvenile stage in natural conditions lasts 2–4 years (Gatsuk et al., 1980).

Woody plants. The duration of the juvenile stage is maximal. In most deciduous species (oak, ash, birch), seedlings retain juvenile traits for 3–7 years, in conifers (spruce, pine) — 5–10 years, and in some tropical trees — up to 15–20 years (Poethig, 2013; Zotz et al., 2011).

Growing seedlings. In protected ground, optimal conditions (light, temperature, nutrition) are created, which makes it possible to shorten the juvenile stage and obtain early products (cucumbers, tomatoes, cabbage). At the same time, pricking out and hardening can temporarily slow down development, stimulating the formation of a more powerful root system.

Grafting of fruit crops. To shorten the juvenile stage (the period before the first fruiting), seedlings (rootstocks) are grafted with cuttings taken from fruit-bearing trees. The scion is already in the virginile or generative phase, which allows obtaining a harvest 2–5 years earlier than from a seedling (Poethig, 2013).

Regulation of mineral nutrition. Nitrogen fertilization accelerates vegetative growth but may delay the transition to the virginile stage in fruit crops. Therefore, in nurseries, nitrogen doses are limited, and potassium-phosphorus fertilizers are applied to accelerate tissue maturation and the transition to fruiting.

Hormonal treatments (in modern agronomy, although this borders on physiology, we mention it without details): treatment with gibberellins can accelerate the transition to the adult state in some species (apple, citrus), while retardants (e.g., paclobutrazol) slow it down.

Change in photosynthetic activity. In many species, adult leaves have higher net photosynthesis per unit area than juvenile leaves (Lawrence et al., 2022 — cited by Liao & Xu, 2026). Juvenile leaves, conversely, are often more efficient under shaded conditions.

Change in water regime and drought tolerance. Adult leaves usually have a thicker cuticle and better regulate transpiration.

Change in hormonal balance. At the molecular level, the transition is mediated by a decrease in miR156 expression and an increase in the activity of SPL transcription factors (Poethig, 2013; Manuela & Xu, 2020). However, since we avoid delving into biochemistry and genetics, this information is provided only for general context.

In annual crops (tomato, cucumber), 1–3 weeks pass between the beginning of the virginile state and the setting of the first flowers.

In biennials (carrot, cabbage), flowering occurs only in the second year after vernalization, whereas the virginile state is achieved already at the end of the first year.

In fruit trees (apple, pear), the virginile state can last 2–5 years or more before the first flowering. During this period, the tree is already capable of vegetative propagation (its cuttings root) and has adult-type leaves, but does not yet bear fruit.

For vegetable growing: determining the optimal age of seedlings for transplanting into the field. Overgrown seedlings (delayed in the juvenile phase due to crowding or lack of light) produce a reduced yield.

For fruit growing: assessing the readiness of seedling rootstocks for budding (grafting with a bud). Grafting is usually carried out when the rootstock has already transitioned to the virginile state — then the scion takes better and enters fruiting faster.

For forestry and ornamental horticulture: selecting cuttings for vegetative propagation. Cuttings from juvenile plants do not root, so harvesting is carried out only from virginile and generative individuals.

For breeding: early culling of hybrids that retain juvenile traits for a long time (especially in fruit crops), because they enter fruiting later.

Resistance to diseases and pests. Testing seedlings for resistance to root rots, powdery mildew, rust, and other diseases is often carried out at the seedling or young plant stage, allowing the culling of susceptible forms without waiting for maturity (Bidlack & Jansky, 2021).

Winter hardiness and drought tolerance. Assessment of tolerance to low temperatures or drought can be carried out on juvenile plants under controlled conditions, which significantly accelerates the breeding process.

Early fruiting (in fruit crops). Seedlings with a short juvenile stage are selected for further propagation, as they enter fruiting earlier and produce earlier yields.

Morphological markers. In some species, the shape of juvenile leaves correlates with economically valuable traits of adult plants (e.g., in maize, the shape of the first leaf may indicate resistance to the stem borer).