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Thorns, spines, and prickles
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Prickles on a blackberry branch

In plant morphology, thorns, spines, and prickles, and in general spinose structures (sometimes called spinose teeth or spinose apical processes), are hard, rigid extensions or modifications of leaves, roots, stems, or buds with sharp, stiff ends, and generally serve the same function: physically defending plants against herbivory.

Description

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In common language, the terms are used more or less interchangeably, but in botanical terms, thorns are derived from shoots (so that they may or may not be branched, they may or may not have leaves, and they may or may not arise from a bud),[1][2][3][4] spines are derived from leaves (either the entire leaf or some part of the leaf that has vascular bundles inside, like the petiole or a stipule),[1][2][3][4] and prickles are derived from epidermis tissue (so that they can be found anywhere on the plant and do not have vascular bundles inside[4]).[1][2][3]

Leaf margins may also have teeth, and if those teeth are sharp, they are called spinose teeth on a spinose leaf margin[1][2] (some authors consider them a kind of spine[2]). On a leaf apex, if there is an apical process (generally an extension of the midvein), and if it is especially sharp, stiff, and spine-like, it may be referred to as spinose or as a pungent apical process[1] (again, some authors call them a kind of spine[2]). When the leaf epidermis is covered with very long, stiff trichomes (more correctly called bristles in this case;[1] for some authors a kind of prickle[2]), it may be referred to as a hispid vestiture;[1][2][3] if the trichomes are stinging trichomes, it may be called a urent vestiture.[1]

There can be found also spines or spinose structures derived from roots.[5]

Function

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The predominant function of thorns, spines, and prickles is deterring herbivory in a mechanical form. For this reason, they are classified as physical or mechanical defenses, as opposed to chemical defenses.

Not all functions of spines or glochids are limited to defense from physical attacks by herbivores and other animals. In some cases, spines have been shown to shade or insulate the plants that grow them, thereby protecting them from extreme temperatures. For example, saguaro cactus spines shade the apical meristem in summer, and in members of the Opuntioideae, glochids insulate the apical meristem in winter.

Agrawal et al. (2000) found that spines seem to have little effect on specialist pollinators, on which many plants rely in order to reproduce.[6]

Definitions and technical distinctions

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Pointing or spinose processes can broadly be divided by the presence of vascular tissue: thorns and spines are derived from shoots and leaves respectively, and have vascular bundles inside, whereas prickles (like rose prickles) do not have vascular bundles inside, so that they can be removed more easily and cleanly than thorns and spines.

Thorns are modified stems and arise from buds
Cactus areoles; shoot (yellow), spines (green) and glochids (also spines, green and little)
(A) Thorn or spine
(B) Prickle
A spinose tooth in a leaf margin
A spinose apical process

Thorns

[edit]

Thorns are modified branches or stems. They may be simple or branched.

Spines

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Spines are modified leaves, stipules, or parts of leaves, such as extensions of leaf veins. Some authors prefer not to distinguish spines from thorns because, like thorns, and unlike prickles, they commonly contain vascular tissue.[7]

Spines are variously described as petiolar spines (as in Fouquieria), leaflet spines (as in Phoenix), or stipular spines (as in Euphorbia), all of which are examples of spines developing from a part of a leaf containing the petiole, midrib, or a secondary vein.[1] The plants of the cactus family are particularly well known for their dense covering of spines. Some cacti have also glochids (or glochidia, singular glochidium) – a particular kind of spine of different origin, which are smaller and deciduous with numerous retrose barbs along its length (as found in areoles of Opuntia).[1]

Prickles

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Prickles are comparable to hairs but can be quite coarse (for example, rose prickles). They are extensions of the cortex and epidermis.[8][9] Technically speaking, many plants commonly thought of as having thorns or spines actually have prickles. Roses, for instance, have prickles.[7] While the position of thorns and spines are known positively to be controlled by phyllotaxis, the positioning of prickles appears to be truly random. If not, then by a phyllotaxis so arcane as to give the appearance of randomness.[citation needed] The largest prickles are found on the trunk and major limbs of Ceiba speciosa which can be 5 cm (2.0 in) long and diameter.

The genus Solanum contains a mixture of species with and without prickles. Phylogenetic analysis in 2024 concluded that members of a gene family known for involvement in cytokinin biosynthesis were involved in prickle production.[10]

Other structures

[edit]

Other similar structures are spinose teeth, spinose apical processes, and trichomes. Trichomes, in particular, are distinct from thorns, spines, and prickles in that they are much smaller (often microscopic) outgrowths of epidermal tissue, and they are less rigid and more hair-like in appearance; they typically consist of just a few cells of the outermost layer of epidermis, whereas prickles may include cortex tissue. Trichomes are often effective defenses against small insect herbivores; thorns, spines, and prickles are usually only effective against larger herbivores like birds and mammals.

Spinescent is a term describing plants that bear any sharp structures that deter herbivory. It also can refer to the state of tending to be or become spiny in some sense or degree, as in: "... the division of the African acacias on the basis of spinescent stipules versus non-spinescent stipules..."[11]

"Root spines" on the trunk of a Cryosophila species.

There are also spines derived from roots, like the ones on the trunk of the "root spine palms" (Cryosophila spp.). The trunk roots of Cryosophila guagara grow downwards to a length of 6–12 cm, then stop growing and transform into a spine.[5] The anatomy of crown roots on this species (roots among the bases of the living fronds) also alters during their life.[5] They initially grow upwards and then turn down and finally they, too, become spinous.[5] Lateral roots on these two types of roots, as well as those on the stilt roots on this species, also become spinous.[5] Some authors believe that some of these short spiny laterals have a ventilating function so they are 'pneumorhizae'.[5] Short spiny laterals that may have a ventilating function may also be found on roots of Iriartea exorrhiza.[5]

There are also spines that function as pneumorhizae on the palm Euterpe oleracea.[5] In Cryosophila nana (formerly Acanthorhiza aculeata), there are spiny roots; some authors prefer to term these "root spines" if the length of the root is less than 10x the thickness and "spine roots" if the length is more than 10x the thickness.[5] Adventitious spiny roots have also been described on the trunks of dicotyledonous trees from tropical Africa (e.g. Euphorbiaceae, as in Macaranga barteri, Bridelia micrantha and B. pubescens; Ixonanthaceae, Sterculiaceae), and may also be found protecting perennating organs such as tubers and corms (e.g. Dioscorea prehensilis -Dioscoreaceae- and Moraea spp. -Iridaceae- respectively).[5] Short root spines cover the tuberous base of the epiphytic ant-plant Myrmecodia tuberosa (Rubiaceae), these probably give protection to ants which inhabit chambers within the tuber as they wander over the plant's surface. (Jackson 1986[5] and references therein). In many respects, the pattern of spine formation is similar to that which occurs in the development of thorns from lateral shoots. (Jackson 1986[5] and references therein).

Evolution

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It has been proposed that thorny structures may have first evolved as a defense mechanism in plants growing in sandy environments that provided inadequate resources for fast regeneration of damage.[12][13]

Morphological variation

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Spinose structures occur in a wide variety of ecologies, and their morphology also varies greatly. They occur as:

Some thorns are hollow and act as myrmecodomatia; others (e.g. in Crataegus monogyna) bear leaves. The thorns of many species are branched (e.g. in Crataegus crus-galli and Carissa macrocarpa).

Human uses

[edit]

Plants bearing thorns, spines, or prickles are often used as a defense against burglary, being strategically planted below windows or around the entire perimeter of a property.[17] They also have been used to protect crops and livestock against marauding animals. Examples include hawthorn hedges in Europe, agaves or ocotillos in the Americas and in other countries where they have been introduced, Osage orange in the prairie states of the US, and Sansevieria in Africa.[18][page needed]

See also

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References

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Bibliography

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Thorns, spines, and prickles

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Thorns, spines, and prickles are sharp, rigid structures that protrude from various , primarily functioning as adaptations for defense against herbivores by deterring or . These structures differ fundamentally in their developmental origins and anatomical composition: thorns arise as modified stems or branches from axillary buds and contain , spines develop from modified leaves, stipules, or other foliar parts and also possess vascular elements, while prickles form as outgrowths of the epidermal layer without internal vascular support, making them more fragile and easily detachable. Despite their shared protective role, the distinctions among these structures reflect diverse evolutionary pathways in , with thorns often being stout and woody—sometimes branched or even bearing leaves—spines typically slender and stiff, and prickles finer and more flexible, akin to hardened hairs. Common examples include thorns on ( spp.) and honey locusts (), spines on cacti (Cactaceae family) and American holly (), and prickles on roses (Rosa spp.) and blackberries ( spp.). In addition to defense, some spines retain photosynthetic capabilities, contributing to the plant's overall resource acquisition in arid environments. The presence of these armaments is widespread across angiosperms and gymnosperms, often concentrated on stems, leaves, or fruits, and their development is genetically regulated— for instance, in thorns, specific genes like TI1 and TI2 suppress activity to promote pointed growth rather than branching; recent (as of 2024) has shown that prickle formation in diverse involves of the WOX , facilitating potential removal in crops like roses and eggplants. While they enhance survival in herbivore-rich ecosystems, these structures can pose challenges in cultivation, such as during or handling, and their absence in certain mutants has been linked to increased branching and fruit yield in crops like . Overall, thorns, spines, and prickles exemplify how have convergently evolved mechanical defenses to balance protection and growth.

Definitions and Distinctions

Thorns

Thorns are sharp, pointed structures in that develop as modified stems or branches, typically arising from axillary buds in the leaf axil. These modifications result in hardened, woody outgrowths that retain the fundamental organization of stem tissue, allowing them to function as integral extensions of the plant's vascular system. Anatomically, thorns can be either hollow or solid and are vascularized, containing for water transport and for nutrient distribution, which connects them directly to the parent stem. In some , thorns remain green and capable of due to the presence of in their epidermal cells, contributing minimally to the plant's overall carbon fixation. Representative examples include the short, straight thorns of plants, such as those on Citrus like Meyer , which emerge from populations and measure up to several centimeters in length. In contrast, hawthorn (Crataegus spp.) produces long, branched thorns, often 1 to 3 inches in size, that develop as woody spikes from branches. Thorns are distinguished from other sharp plant structures by their homology to stems, including vascular continuity, whereas spines and prickles arise from different tissues and lack such stem-like .

Spines

Spines are rigid, pointed structures in that develop from modified leaves, stipules, petioles, or other foliar components, distinguishing them through their embryological origins in leaf primordia rather than stem tissue. In maturity, while some spines, particularly in cacti, lose vascular continuity with the main stem and lack functional or , many spines retain vascular elements or connections derived from their foliar origin. Anatomically, spines are reinforced for rigidity by dense sclerenchyma tissue, including fibers that form a tough core, often surrounded by a hardened composed of sclereid-like cells. While many spines, particularly in arid-adapted species, lack extensive internal vascular elements, some retain traces of leaf venation as remnants of their foliar heritage. Prominent examples include the spines of cacti such as those in the genus , where entire leaves are transformed into clusters of sharp, protective projections arising in the axils of microscopic rudimentary leaves. Similarly, in barberry species like , the pointed tips of leaves or modified stipules serve as spines, emerging alongside clusters of smaller leaves. In terms of homology, spines are derived from foliar organs and thus share developmental pathways with leaves, in contrast to thorns which originate from axillary buds on stems. Although spines may superficially resemble thorns in appearance, their distinct foliar underscores a key botanical differentiation.

Prickles

Prickles are sharp, pointed extensions formed from the and cortex of stems, leaves, or other surfaces, without derivation from modified stems or leaves. These structures represent multicellular outgrowths that lack homology to specific organs, setting them apart from thorns and spines. Anatomically, prickles are composed solely of epidermal cells, sometimes incorporating cortical tissue for reinforcement, and contain no internal vascular tissue such as or . This non-vascular composition renders them superficial and easily detachable, often peeling away with the without affecting the plant's underlying woody structure. Representative examples of prickles occur on rose bushes (Rosa spp.) and blackberry canes (Rubus spp.), where these epidermal projections provide a defensive barrier despite their fragile attachment. In plants like roses, prickles may appear visually similar to thorns and spines but remain distinct due to their epidermal origin and absence of organ modification. In botany, trichomes represent epidermal outgrowths that can resemble sharp defensive structures but differ fundamentally from thorns, spines, or prickles in their typically unicellular or multicellular, non-woody composition derived solely from dermal tissue. These hair-like appendages, initiated as protuberances from epidermal cells, vary from soft filaments to rigid, pointed forms that provide mechanical protection without vascular integration. For instance, the stinging hairs of nettles (Urtica spp.) are specialized glandular trichomes containing irritants like formic acid and histamine, which penetrate skin upon contact but lack the rigidity of true spines. Aculei, often described as hollow or hardened prickles in certain plant groups, are sharp projections confined to the epidermis, distinguishing them from vascular-derived structures like thorns or spines. In some palms (Arecaceae), aculei appear as solitary or sparse, recurved points along petioles or leaf margins, serving as lightweight deterrents without penetrating deeper tissues. These are etymologically rooted in Latin for "stings" and historically applied to epidermal armatures in brambles and palms, but modern usage clarifies their non-vascular nature to avoid conflation with sturdier spines. Stipules, when modified into spiny forms, form paired, sharp appendages at the base that originate from tissue rather than stems or epidermis alone, thus qualifying as spine variants in some classifications. Unlike non-spiny stipules, which are scale-like or membranous, these rigid structures—seen in genera like —emerge from the stipular primordia and retain vascular connections, emphasizing their foliar derivation. Technical distinctions among these related structures hinge on tissue origin: trichomes and aculei arise from the dermal layer (), lacking or , whereas spiny stipules derive from of leaf parts, incorporating vascular elements akin to true spines. Glochids in cacti ( subfamily) exemplify hair-like, barbed spines that overlap with true spines but are distinct as , tufted outgrowths from areoles, often functioning as fine irritants rather than rigid barriers. Historical in has been fraught with inconsistencies, as early descriptors like "acantha" or "aculeus" were applied vaguely to any sharp plant projection, leading to terminological overlap until 19th-century systematists like Lindley delineated origins based on anatomy. This evolution underscores the importance of ontogenetic criteria—such as epidermal versus —to resolve ambiguities in classifying sharp plant armatures.

Functions and Adaptations

Defensive Mechanisms

Thorns, spines, and prickles function primarily as physical barriers that deter from accessing plant tissues, thereby reducing rates of and . These structures inflict injury or hinder efficient feeding, with experimental evidence showing substantial deterrence; for example, removal of thorns from Acacia drepanolobium increased mammalian threefold, implying thorns mitigate approximately two-thirds of potential herbivory. Similarly, spiny architectures in certain plants, such as divaricate juveniles, result in 30–70% less loss compared to non-spiny forms under herbivore pressure. Key defensive mechanisms involve impalement of mouthparts or skin during feeding attempts, which causes pain and bleeding, and entanglement that restricts movement and prolongs exposure to predators. In Acacia tortilis, increasing spine density forces goats to adopt less efficient feeding strategies, such as biting entire twigs rather than selectively grazing leaves, thereby protecting meristems and foliage. Some spines also associate with irritants; the barbed glochids of Opuntia species embed in tissues, provoking inflammation and deterring herbivores by causing discomfort, including potential eye irritation upon close contact. In swollen-thorn acacias like Vachellia cornigera, thorns hollowed into domatia house symbiotic ants, combining physical impalement with behavioral defense; the ants swarm and sting intruders, often halting browsing within seconds when paired with the thorns' barrier effect. This mutualism exemplifies how these structures enhance overall deterrence beyond mere physical hindrance. Fossil records provide ecological evidence of their anti-herbivore role, with spiny leaf impressions appearing in Eocene deposits from subtropical Asia, coinciding with the rise of mammalian browsers and indicating early adaptation to avoid feeding damage through physical defense.

Non-Defensive Roles

In addition to their well-known protective roles, thorns, spines, and prickles fulfill several non-defensive functions that enhance plant survival and adaptation in various environments. One prominent role is providing structural support, particularly for climbing species. In climbing roses (Rosa spp.), prickles act as hooks that anchor stems to supporting vegetation or structures, facilitating upward growth without the need for specialized tendrils; this downward-oriented hook structure develops through differential growth during stem maturation, allowing the plant to secure itself loosely while minimizing damage upon detachment. Similarly, in brambles such as blackberry (Rubus spp.), curved prickles on arching stems aid in scrambling and attachment to nearby plants, enabling the vine to reach sunlight and expand its range by leveraging existing supports. These attachment mechanisms are especially vital in dense vegetation, where prickles prevent slippage and promote efficient resource acquisition. Physiological benefits are another key non-defensive contribution, particularly in for arid-adapted plants. Spines on cacti, such as those in the genus , create shade over the stem surface, significantly reducing rates by limiting direct solar exposure and lowering surface temperatures; this shading effect can decrease water loss in some species under intense desert conditions. Additionally, these spines disrupt wind currents around the plant body, further minimizing evaporative loss in exposed, arid habitats like the . Thorns, spines, and prickles also play supportive roles in reproduction by safeguarding developing reproductive structures from environmental stresses. In some arid , spines around flower clusters, as seen in certain cacti, reduce physical abrasion from wind or sand, preserving floral integrity and promoting successful and fruit set. These functions highlight the multifunctional nature of these structures, where support overlaps with in challenging habitats.

Evolutionary Origins

Developmental Pathways

Thorns develop through meristematic activity in axillary buds or modified stem branches, where undifferentiated cells in the shoot apical proliferate to form sharp, pointed structures instead of typical lateral shoots. In contrast, spines arise from the suppression of normal development in primordia or stipules, resulting in hardened, pointed remnants of foliar organs that lack further expansion. Prickles, however, originate from localized in the and underlying subepidermal tissues, leading to multicellular outgrowths without vascular connections to the stem. Genetic regulation of thorn formation involves class I KNOX transcription factors, such as THORN IDENTITY1 (TI1) in Citrus, an ortholog of the Arabidopsis BREVIPEDICELLUS (BP) gene, which maintains meristematic identity and suppresses leaf-like differentiation in bud primordia. For spines, auxin signaling plays a key role, as demonstrated in cucumber (Cucumis sativus) where the NUMEROUS SPINES (NS) gene encodes an auxin influx carrier (AUX1-like) that modulates auxin distribution to promote epidermal cell division and spine initiation on fruits. Recent studies using cucumber as a model have confirmed that disruptions in this auxin transport pathway reduce spine density by altering local hormone gradients during primordia development. Hormonal influences further shape these structures, with gibberellins promoting prickle density in roses (Rosa spp.) by enhancing epidermal cell expansion and secondary wall thickening during outgrowth formation. In rose stems, gibberellin application increases prickle number and size, likely through upregulation of genes involved in similar to those in development. Laboratory evidence from mutagenesis experiments underscores the reversibility of these developmental pathways. In , targeted mutations in the TI1 KNOX gene transform thorns into functional branches, with over 10% of modified structures exhibiting and flower production, demonstrating how genetic tweaks can redirect fate. Similarly, in species, loss-of-function mutations in the LONELY GUY (LOG) biosynthetic gene independently eliminate prickles across multiple lineages, confirming hormone-dependent control and enabling prickle-free variants through breeding. These experiments highlight the plasticity of sharp structure formation, where altering key regulatory genes or hormones can suppress or repurpose them without compromising plant viability.

Phylogenetic Patterns

Thorns, spines, and prickles represent polyphyletic traits that have arisen through across multiple plant lineages, particularly within angiosperms, where they serve primarily as anti-herbivore defenses. In the family , thorns—modified stems—evolved independently in lineages like , emerging as axillary short shoots that provide protection against browsing mammals. Similarly, in Cactaceae, spines—derived from modifications—developed convergently as part of the family's adaptation to arid environments, with evidence indicating their presence from the Eocene onward. This repeated underscores the non-homologous nature of these structures, with prickles (epidermal outgrowths) showing at least 28 independent origins across vascular plants via co-option of ancient gene families like LOG, which regulate biosynthesis. Molecular phylogenetic analyses suggest the origins of some spinose lineages in the , approximately 100 million years ago, coinciding with the radiation of flowering and the rise of herbivorous dinosaurs, but direct fossil evidence appears later in the , such as thorn-like modifications in Eocene Rosaceae fossils from North American deposits. Over subsequent epochs, independent acquisitions occurred in more than 20 families, with spines alone evolving multiple times in eudicot woody , comprising about 11.5% of woody in southern African savannas. Prickles, in particular, trace back over 400 million years but proliferated in angiosperms post-Cretaceous, with losses and regains documented in lineages like . Phylogenetic patterns reveal a higher prevalence of these structures in dry biomes and herbivore-rich ecosystems, such as savannas and deserts, where they enhance survival against large mammals and promote diversification through intercontinental migrations. For instance, in , spines evolved convergently in arid-adapted genera like , aiding water conservation and defense in open habitats. In contrast, exhibits thorns in acacia-like species within African and Australian savannas, where they correlate with intense browsing pressure from ungulates, illustrating how environmental selection drives polyphyletic spinescence.

Morphological Diversity

Structural Variations

Thorns, spines, and prickles exhibit a range of structural forms that reflect their developmental origins and adaptive modifications. Thorns, derived from stems or branches, can be simple or branched; for instance, in the honey locust (Gleditsia triacanthos), simple thorns up to 20 cm long occur along the trunk, while branched thorns with multiple arms arise from the bark, providing complex architectures. Spines, typically modified leaves, often appear as straight, needle-like projections, though some species display curved or hooked variants to enhance attachment or deterrence. However, some spines, such as those in cacti, lack vascular tissue and are composed entirely of sclerenchyma. Prickles, epidermal outgrowths, are generally simpler and unbranched but can include barbed forms, such as the barbed awns (modified foliar spines) on certain grass inflorescences like those in Hordeum species, where backward-facing barbs aid in seed dispersal. Tissue composition varies significantly among these structures, influencing their rigidity and functionality. Thorns and spines are typically lignified, consisting of vascular tissues including xylem and phloem embedded in sclerenchyma, which imparts stiffness and durability; for example, cactus spines consist of sclerenchymatous tissue surrounded by lignified sclereids for structural support, but lack vascular tissue. In contrast, prickles are often less lignified and more flexible, primarily composed of epidermal and cortical cells rich in cellulose and suberin, though some, like those in roses, incorporate lignin for added hardness. Additional modifications include the presence of glands on certain spines, such as resin-secreting structures in some Euphorbia species, or terminal hooks on thorns in climbing plants like Asparagus falcatus, formed from fused leaf and stem tissues. Representative examples highlight these variations. Needle-like spines in cacti such as Echinopsis terscheckii are straight, non-barbed, and cylindrical, with smooth surfaces derived from hardened epidermal layers. In contrast, the barbed spines of feature backward-projecting barbs along their length, composed of overlapping epidermal cells that facilitate anchoring. For thorns, Gleditsia triacanthos displays stout, sometimes flattened basal structures that branch into multiple pointed tips, lignified throughout for robustness. Environmental factors, particularly , can induce structural modifications in these defenses. In shrubs like Lycium ruthenicum, water deficit triggers phenotypic plasticity, leading to increased thorn density and branched forms through epigenetic changes such as DNA hypermethylation, resulting in denser coverage on stems under arid conditions. This plasticity underscores how abiotic stresses shape morphological diversity across taxa, often converging on similar spinescent forms independently in arid-adapted lineages.

Size and Distribution Patterns

Thorns, spines, and prickles exhibit a wide range of sizes, typically scaling with the overall dimensions of the host plant to optimize defensive efficacy. Prickles, as epidermal outgrowths, are generally the smallest, ranging from less than 1 mm to about 5 mm in length, as seen in species like roses (Rosa spp.) where they form dense, short coverings on stems. Spines, derived from modified leaves or stipules, often measure 1–5 cm, while thorns, which are modified stems or branches, can reach up to 10 cm or more, such as the 3–10 cm axillary thorns on honey locust (Gleditsia triacanthos). This variation correlates with plant stature; larger woody species tend to produce longer and thicker structures to deter bigger herbivores. Density patterns of these structures vary by plant architecture and environmental context, often clustering at vulnerable nodes or branch tips for targeted protection, though some species display uniform distributions along stems. For instance, in shrubs like Sarcopoterium spinosum, thorn density can average 6,000–11,000 per square meter of canopy area, concentrated at stem nodes to maximize coverage against browsers. correlations show higher densities in arid regions, where limitation favors compact, heavily armed growth forms; shrubs often exhibit thorn or spine densities exceeding those in mesic forests by 2–3 times, enhancing anti-herbivore defenses in resource-scarce habitats. Globally, spiny structures occur in approximately 12% of woody angiosperm , based on analyses of large-scale trait databases incorporating records. Regional surveys reinforce this prevalence: in Mediterranean floras like Italy's, about 5% of the total taxa (401 ) bear thorns, spines, or prickles, predominantly in woody forms. Hotspots for these traits align with arid and semi-arid zones, including the Mediterranean basin and subtropical deserts, where up to 18–20% of woody may be , driven by elevated pressure. Herbarium-based surveys highlight correlations between spinescence prevalence and ecological pressures, such as historical large-mammal herbivory. Data from global repositories like the TRY database, drawing on millions of digitized specimens, indicate that spine-bearing lineages are overrepresented in regions with past high densities of browsers (>20 kg body mass), with positive associations in 70% of analyzed biomes. These patterns underscore how quantitative traits like size and density evolve as responses to selective forces, rather than random distributions.

Human Applications

Agricultural and Horticultural Uses

In agricultural practices, particularly in African pastoralism, thorny hedges serve as effective natural barriers to manage and protect crops from grazing animals. Dense plantings of thorny species like spp. create impenetrable fences that deter and wildlife, reducing conflicts between pastoralists and farmers while allowing for sustainable land use in arid regions. For instance, Maasai communities in utilize branches of thorny acacias for fencing, which confines and minimizes on communal lands. Spiny rootstocks play a crucial role in , enhancing disease resistance and overall vigor in horticultural cultivation. The (Poncirus trifoliata), a spiny relative, is widely used as a for commercial varieties due to its tolerance to caused by spp. and resistance to nematodes, enabling healthier trees in disease-prone soils. This 's thorny growth, when it emerges above the graft union, must be pruned to prevent dominance over the desired fruiting scion, but its underground system provides long-term stability and productivity in orchards. Prickly plants such as blackberries ( spp.) are employed in erosion control strategies within horticultural and agricultural landscapes, leveraging their extensive root systems to stabilize on slopes and riverbanks. In riparian areas, blackberry hedges bind particles, reducing runoff and loss during heavy rains, though care must be taken with invasive varieties to avoid ecological disruption. In programs, selective genetic modifications have targeted the removal of prickles from varieties in the (Solanaceae) to improve harvest efficiency and worker safety in commercial agriculture. Recent advances as of 2024, including CRISPR-Cas9 editing of LOG genes, have successfully produced prickle-free variants in species such as aubergines and wild nightshades, maintaining yield while eliminating defensive spines that hinder mechanical harvesting. These edits, demonstrated in studies on plants, represent a high-impact contribution to sustainable production by reducing labor costs and injury risks without compromising plant vigor.

Ornamental and Industrial Applications

Thorny plants are widely utilized in for their dual role in and , particularly as hedges that deter intruders while enhancing urban designs. , with its vibrant bracts and sharp thorns, is a popular choice for creating impenetrable barriers in residential and public spaces, such as along fences or walls in tropical and subtropical regions. This application combines ornamental appeal with practical defense, as the plant's climbing habit allows it to cover structures effectively, reducing the need for additional . In traditional crafts, cactus spines have served as natural tools, especially among for and other precise work. For instance, spines from prickly pear cacti were harvested, cleaned, and sharpened to function as needles for stitching hides, baskets, and clothing, valued for their durability and availability in arid environments. This practice highlights the utilitarian adaptation of spines beyond defense, integrating them into daily artisanal activities. Industrial applications of prickles and related structures are emerging in bio-materials, where thorny derivatives contribute to sustainable composites and fibers. Prickles from like raspberries or blackberries can be processed into natural reinforcements for eco-friendly polymers, enhancing tensile strength in applications such as or insulation, though extraction challenges limit widespread adoption. Ornamental breeding programs select for visually striking traits, including color-contrasting spines in cacti genera like , to appeal to collectors and landscapers, often pairing white or yellow spines with colorful pads for heightened aesthetic value. Culturally, thorns and spines carry symbolic weight in and festivals, representing resilience, protection, and sacrifice. In medieval European , the thorn often symbolized martyrdom or divine suffering, as seen in motifs like the crown of thorns associated with Christian . During festivals such as the Holy Thorn Ceremony in , , hawthorn branches—evoking the legendary thorn tree linked to —are paraded to honor religious heritage and community identity. These uses underscore thorns' role in evoking themes of endurance across traditions.

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