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In
plant morphology Phytomorphology is the study of the physical form and external structure of plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy ...

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 A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. The leaves, stem, flower and fruit together form the shoot system. Leaves are ...

leaves
,
root In vascular plant Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from Greek τραχεῖα ἀρτηρία ''trācheia artēria'' 'windpipe' + φυτά ''phutá'' 'plants'), form a large grou ...

root
s,
stems
stems
or
buds In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the A ...

buds
with sharp, stiff ends, and generally serve the same function: physically deterring animals from eating the plant material.


Description

In common language the terms are used more or less interchangeably, but in botanical terms, thorns are derived
shoot In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Anci ...

shoot
s (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),Simpson, M. G. 2010. "Plant Morphology". In: ''Plant Systematics, 2nd. edition''. Elsevier Academic Press. Chapter 9.Judd, Campbell, Kellogg, Stevens, Donoghue. 2007. "Structural and Biochemical Characters". In: ''Plant Systematics, a phylogenetic approach, third edition''. Chapter 4.Turner et al. 2005, ''Sonoran Desert Plants, an Ecological Atlas.'' University of Arizona Press.
/ref>Van Wyk, Van Wyk. 2007. ''How to identify trees in South Africa.'' Struik.
/ref> spines are derived from
leaves A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. The leaves, stem, flower and fruit together form the shoot system. Leaves are ...

leaves
(either the entire leaf or some part of the leaf that has vascular bundles inside, like the
petiole Petiole may refer to: *Petiole (botany), the stalk of a leaf, attaching the blade to the stem *Petiole (insect anatomy), the narrow waist of some hymenopteran insects {{disambiguation ...
or a
stipule In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancien ...
), and prickles are derived from
epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of animal Animals (also calle ...
tissue (so that they can be found anywhere on the plant and do not have vascular bundles inside). Leaf margins may also have teeth, and if those teeth are sharp, they are called spinose teeth on a spinose
leaf margin A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. The leaves, stem, flower and fruit together form the shoot system. Leaves are ...
(some authors consider them a kind of spine). 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'' (again, some authors call them a kind of spine). When the leaf epidermis is covered with very long, stiff
trichome Trichomes ( or ), from the Greek language, Greek τρίχωμα (trichōma) meaning "hair", are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, gland ...
s (more correctly called
bristle A bristle is a stiff hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, ...
s in this case; for some authors a kind of prickle), it may be referred to as a ''hispid vestiture''; if the trichomes are stinging trichomes, it may be called a ''urent vestiture''. There can be found also spines or spinose structures derived from roots.


Function

The predominant function of thorns, spines, and prickles is deterring
herbivory A herbivore is an animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All ...
in a mechanical form. For this reason, they are classified as physical or mechanical defenses, as opposed to
chemical A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which ...
defenses. Not all functions of spines or
glochid Glochids or glochidia (singular "glochidium") are hair-like spines or short prickles, generally barbed, found on the areole In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of b ...
s 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 The saguaro (, ) (''Carnegiea gigantea'') is a tree-like cactus A cactus (plural cacti, cactuses, or less commonly, cactus) is a member of the plant Plants are predominantly photosynthetic Photosynthesis is a process used by p ...

saguaro cactus
spines shade the
apical meristem The meristem is a type of tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North America * ''Triphosa du ...
in summer, and in members of the
Opuntioideae Opuntioideae is a subfamily In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying groups of biological organisms based on shared chara ...
, 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.


Definitions and technical distinctions

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 A rose is a woody perennial plant, perennial flowering plant of the genus ''Rosa'', in the family Rosaceae, or the flower it bears. There are over three hundred Rose species, species and Garden roses, tens of thousands of cultivars. They form ...

rose
prickles) do not have vascular bundles inside, so that they can be removed more easily and cleanly than thorns and spines.


Thorns

Thorns are modified branches or . They may be simple or branched. File:thorn image.JPG, Smooth, featureless ''
Citrus ''Citrus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circums ...

Citrus
'' thorn. File:Gymnosporia buxifolia thorn.JPG, '' Gymnosporia buxifolia'' thorn, its leaves, nodes, and emergence from an axillary bud demonstrating its nature as a branch. File:Carissa bispinosa Uniondale 1167.jpg, ''
Carissa bispinosa ''Carissa bispinosa'' grows as a shrub or small tree up to tall. Its fragrant flowers feature a white Corolla (flower), corolla. The fruit is red when ripe. Its habitat is woodland and forest from to altitude. Vernacular names for the plant inc ...
'' showing characteristic branched thorns.


Spines

Spines are modified
leaves A leaf (plural leaves) is the principal lateral appendage of the vascular plant plant stem, stem, usually borne above ground and specialized for photosynthesis. The leaves, stem, flower and fruit together form the shoot system. Leaves are ...

leaves
,
stipules In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancien ...
, 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 Vascular tissue is a complex conducting tissue Tissue may refer to: Biology * Tissue (biology), an ensemble of similar cells that together carry out a specific function * ''Triphosa haesitata'', a species of geometer moth found in North Ameri ...
.Bell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K
preview in google books
/ref> Spines are variously described as petiolar spines (as in ''
Fouquieria ''Fouquieria'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circu ...
''), leaflet spines (as in '' Phoenix''), or stipular spines (as in ''
Euphorbia ''Euphorbia'' is a very large and diverse genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscr ...

Euphorbia
''), all of which are examples of spines developing from a part of a leaf containing the petiole, midrib, or a secondary vein. The plants of the are particularly well known for their dense covering of spines. Some cacti have also
glochid Glochids or glochidia (singular "glochidium") are hair-like spines or short prickles, generally barbed, found on the areole In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of b ...
s (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
areole In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the A ...
s of ''
Opuntia ''Opuntia'', commonly called prickly pear, is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circu ...

Opuntia
''). File:Ocotillothron02262006.JPG, The spines of ''
Fouquieria splendens ''Fouquieria splendens'' (commonly known as ocotillo (), but also referred to as coachwhip, candlewood, slimwood, desert coral, Jacob's staff, Jacob cactus, and vine cactus) is a plant indigenous to the Sonoran Desert and Chihuahuan Desert and ...

Fouquieria splendens
'' develop from the leaf petioles. File:AcaciaXanthophloeaSpines.JPG, Stipule spines on ''''. File:Pereskia grandifolia ies.jpg, Areoles and spines of the tree-like '' Rhodocactus grandifolius''. File:Fish hook Cactus Without wool.jpg, Spines of ''
Mammillaria ''Mammillaria'' is one of the largest genera in the cactus family In human society A society is a Social group, group of individuals involved in persistent Social relation, social interaction, or a large social group sharing the sa ...
balsasoides'' File:With seperate hook.jpg, Hooked spine of ''Mammillaria balsasoides''


Prickles

Prickles are comparable to hairs but can be quite coarse (for example, rose prickles). They are extensions of the
cortex Cortex or cortical may refer to: Science Anatomy * Cortex (anatomy), the outermost or superficial layer of an organ * Cortex (hair), the middle layer of a strand of hair * Adrenal cortex, the portion of the adrenal gland that produces cortisol and ...
and
epidermis The epidermis is the outermost of the three layers that comprise the skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate Vertebrates () comprise all species of animal Animals (also calle ...
. Technically speaking, many plants commonly thought of as having thorns or spines actually have prickles.
Rose A rose is a woody perennial plant, perennial flowering plant of the genus ''Rosa'', in the family Rosaceae, or the flower it bears. There are over three hundred Rose species, species and Garden roses, tens of thousands of cultivars. They form ...

Rose
s, for instance, have prickles. File:Wait-a-bit stem.jpg, Raised prickles on the stem of '' Caesalpinia decapetala''. File:Rose Prickles.jpg,
Rose A rose is a woody perennial plant, perennial flowering plant of the genus ''Rosa'', in the family Rosaceae, or the flower it bears. There are over three hundred Rose species, species and Garden roses, tens of thousands of cultivars. They form ...

Rose
prickles. File:Solanum viarum 1673056.jpg, Prickles on the leaves of '' Solanum viarum''.


Other structures

Other similar structures are spinose teeth, spinose apical processes, and trichomes.
Trichome Trichomes ( or ), from the Greek language, Greek τρίχωμα (trichōma) meaning "hair", are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, gland ...
s, 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. File:Hulst getand blad Ilex aquifolium.jpg, Spinose leaf margin in ''
Ilex aquifolium ''Ilex aquifolium'', the holly, common holly, English holly, European holly, or occasionally Christmas holly, is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an orga ...

Ilex aquifolium
''. File:Sansevieria trifasciata2.jpg, Spinose apical process in ''
Sansevieria ''Sansevieria'' is a historically recognized genus of flowering plants, native to Africa, notably Madagascar, and southern Asia, now included in the genus ''Dracaena (plant), Dracaena'' on the basis of Molecular phylogenetics, molecular phylogen ...

Sansevieria
''. File:Galium.aparine.jpg, Stiff, sharp trichomes in ''
Galium aparine ''Galium'' is a large genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), ci ...

Galium aparine
''. File:Urtica dioica stinging hair.jpg, Stinging trichome in ''
Urtica dioica ''Urtica dioica'', often known as common nettle, burn nettle, stinging nettle (although not all plants of this species sting) or nettle leaf, or just a nettle or stinger, is a herbaceous Herbaceous plants are vascular plants that have no p ...

Urtica dioica
''.
''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..." There are also spines derived from roots, like the ones on the trunk of the "Root Spine Palms" (''
Cryosophila ''Cryosophila'' is a genus of medium-sized fan palms that range from central Mexico to northern Colombia. Species in the genus can be readily distinguished from related genera by their distinctive downward-pointing Thorns, spines, and prickles, ...
'' spp.). The trunk roots of '' Cryosophila guagara'' grow downwards to a length of 6–12 cm, then stop growing and transform into a spine.Jackson, M. B. (ed.) 1986. ''New Root Formation in Plants and Cuttings.'' Series ''Developments in plant and soil sciences'' nº 20. Martinus Nijhoff Publishers, a member of the Kluwer Academic Publishers Group. Da ordrecht / Boston / Lancaster. p.80-81. https://books.google.com/books?id=gAv8CAAAQBAJ&pg=PA80 The anatomy of crown roots on this species (roots among the bases of the living fronds) also alters during their life. They initially grow upwards and then turn down and finally they, too, become spinous. Lateral roots on these two types of roots, as well as those on the stilt roots on this species, also become spinous. Some authors believe that some of these short spiny laterals have a ventilating function so they are 'pneumorhizae'. Short spiny laterals that may have a ventilating function may also be found on roots of '' Iriartea exorrhiza''. There are also spines that function as pneumorhizae on the palm ''
Euterpe oleracea Euterpe (; el, Εὐτέρπη, lit=rejoicing well' or 'delight , from grc, εὖ, eû, well + el, τέρπειν, térpein, to please) was one of the Muses In ancient Greek religion and mythology, the Muses ( grc, Μοῦσαι, Moûsai, e ...
''. In '' Cryosophila nana'' (formerly ''Acanthorhiza aculeata'') there are spine roots or root spines, some authors may prefer "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. 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 ''Bridelia micrantha'', the mitzeeri or the coastal golden-leaf, is a tree in the family Phyllanthaceae and is native to tropical and southern Africa as well as to the island of Réunion in the Indian Ocean. Description A medium to tall tree (u ...
'' 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 ''Moraea'', the Cape tulips, is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (ta ...
'' spp. -Iridaceae- respectively). 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 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 and references therein).


Evolution

It has been proposed that thorny structures may have first evolved as a
defense mechanism In psychoanalytic theory, a defence mechanism (American English: defense mechanism), is an Unconscious mind, unconscious psychological operation that functions to protect a person from anxiety-producing thoughts and feelings related to interna ...
in plants growing in sandy environments that provided inadequate resources for fast regeneration of damage.


Morphological variation

Spinose structures occur in a wide variety of ecologies, and their morphology also varies greatly. They occur as: * sharpened branches (e.g. in ''
Carissa ''Carissa'' is a genus of shrubs or small trees native to tropical and subtropical regions of Africa, Australia and Asia. Until recently about 100 species were listed, but most of them have been relegated to the status of synonyms or assigned t ...

Carissa
'', ''
Citrus ''Citrus'' is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circums ...

Citrus
'', ''
Crataegus ''Crataegus'' (), commonly called hawthorn, quickthorn, thornapple, Voss, E. G. 1985. ''Michigan Flora: A guide to the identification and occurrence of the native and naturalized seed-plants of the state. Part II: Dicots (Saururaceae–Cornacea ...

Crataegus
''), * spiky inflorescences ('' Tylecodon''), * a tiny point at the tip of the leaf (mucronate leaves) (''
Sansevieria ''Sansevieria'' is a historically recognized genus of flowering plants, native to Africa, notably Madagascar, and southern Asia, now included in the genus ''Dracaena (plant), Dracaena'' on the basis of Molecular phylogenetics, molecular phylogen ...

Sansevieria
''), * leaves fully converted to spines (''
Opuntia ''Opuntia'', commonly called prickly pear, is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circu ...

Opuntia
''), * stipules converted to spines (many ''
Vachellia ''Vachellia'' is a genus of flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Any ...

Vachellia
''), * prickles on stems (''
Rosa Rosa or De Rosa may refer to: People *Rosa (given name) Rosa is a female given name, especially in the Portuguese language, Portuguese, Italian language, Italian and Spanish language, Spanish languages. It may refer to: *''Rosa de Lima'', or Ro ...

Rosa
'', ''
Erythrina ''Erythrina'' is a genus of flowering plants in the pea family, Fabaceae. It contains about 130 species, which are distributed in Tropics, tropical and Subtropics, subtropical regions worldwide. They are trees, with the larger species growing u ...
'' and ''
Ceiba speciosa ''Ceiba speciosa'', the floss silk tree (formerly ''Chorisia speciosa''), is a species of deciduous tree native to the tropical and subtropical forests of South America. It has several local common names, such as ''palo borracho'' (in Spanish la ...

Ceiba speciosa
''), * urticating (i.e. stinging) hairs, * bristles, and * finely barbed spines called
glochid Glochids or glochidia (singular "glochidium") are hair-like spines or short prickles, generally barbed, found on the areole In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of b ...
s. Some thorns are hollow and act as myrmecodomatia; others (e.g. in ''
Crataegus monogyna ''Crataegus monogyna'', known as common hawthorn, oneseed hawthorn, or single-seeded hawthorn, is a species of flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "an ...

Crataegus monogyna
'') bear leaves. The thorns of many species are branched (e.g. in '''' and '''').


Human uses

Plants bearing thorns, spines, or prickles are often used as a defense against
burglary Burglary, also called breaking and entering and sometimes housebreaking, is illegally entering a building or other areas to commit a crime. Usually that offence is theft, but most jurisdictions include others within the ambit of burglary. To co ...
, being strategically planted below windows or around the entire perimeter of a property. They also have been used to protect crops and livestock against marauding animals. Examples include hedges in Europe,
agave ''Agave'' (, , ) is a genus Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), ...

agave
s in the Americas and in other countries where they have been introduced,
Osage orange ''Maclura pomifera'', commonly known as the Osage orange, horse apple, hedge, or hedge apple tree, is a small deciduous In the fields of horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ...
in the prairie states of the US, and ''
Sansevieria ''Sansevieria'' is a historically recognized genus of flowering plants, native to Africa, notably Madagascar, and southern Asia, now included in the genus ''Dracaena (plant), Dracaena'' on the basis of Molecular phylogenetics, molecular phylogen ...

Sansevieria
'' in Africa.Hunter, J. A., "Hunter" Publisher: Buccaneer Books, 1993,


See also

*
Areole In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the A ...
*
Glochid Glochids or glochidia (singular "glochidium") are hair-like spines or short prickles, generally barbed, found on the areole In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of b ...
*
Trichome Trichomes ( or ), from the Greek language, Greek τρίχωμα (trichōma) meaning "hair", are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, gland ...
*
Plant defense against herbivory Plant defense against herbivory or host-plant resistance (HPR) describes a range of adaptation In , adaptation has three related meanings. Firstly, it is the dynamic evolutionary process that fits s to their environment, enhancing their . ...


References


Bibliography

* Simpson, M. G. 2010. "Plant Morphology". In: ''Plant Systematics, 2nd. edition''. Elsevier Academic Press. Chapter 9. * Judd, Campbell, Kellogg, Stevens, Donoghue. 2007. "Structural and Biochemical Characters". In: ''Plant Systematics, a phylogenetic approach, third edition''. Chapter 4. *Esau, K. 1965. ''Plant Anatomy'', 2nd Edition. John Wiley & Sons. 767 pp. *Llamas, K. A. 2003. ''Tropical Flowering Plants''. Timber Press, Portland. 423 pp.


External links

* {{DEFAULTSORT:Thorns, Spines, And Prickles
Plant morphology ''Plant morphology'' is the field in botany that studies the diversity in forms, with the naked eye or slight optical magnification. This is opposed to plant anatomy (see :Plant anatomy) that needs to cut into plants to be able to study its subject, ...
Biological defense mechanisms Hazards of outdoor recreation