Editing Cactus (section)

{{Short description|Family of mostly succulent plants, adapted to dry environments}}
{{About|the plant family}}
{{Redirect|Cacti|the software|Cacti (software)|the album|Cacti (album){{!}}''Cacti'' (album)}}
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{{Automatic taxobox
| fossil_range = {{fossil range|35|0}}Late [[Eocene]] - Recent
| image = <div class="center"><imagemap>
File:Various Cactaceae.jpg|275px
poly 1 743 270 749 299 461 517 314 597 0 5 0 [[Opuntia cochenillifera]]
poly 270 750 318 849 600 842 521 314 303 462 [[Cephalocereus senilis]]
poly 599 3 521 308 603 849 755 1094 739 1513 793 1570 942 1566 948 1041 1118 1020 1295 673 1283 506 1167 482 1208 313 1298 146 1277 0 [[Carnegiea gigantea]]
poly 1166 481 1401 526 1650 463 1653 3 1281 0 1300 143 1210 311 [[Mammillaria longimamma]]
poly 1 744 2 1465 94 1421 143 1357 211 1330 292 1386 267 1241 208 1029 327 863 267 749 [[Rhipsalis paradoxa]]
poly 296 1383 211 1028 328 864 324 851 597 844 751 1091 741 1377 [[Ferocactus hamatacanthus]]
poly 1122 1022 1277 1082 1416 1111 1654 1098 1654 465 1401 526 1287 506 1296 675 [[Echinopsis oxygona]]
poly 950 1042 942 1564 897 1569 909 1820 985 1810 1071 1737 1103 1808 1283 1798 1458 1762 1549 1846 1654 1844 1654 1099 1416 1113 1279 1083 1119 1022 [[Selenicereus grandiflorus]]
poly 1 1905 157 1893 261 1920 286 2363 2 2361 [[Echinocereus pectinatus]]
poly 264 1920 159 1890 1 1906 2 1469 94 1422 144 1355 210 1330 290 1384 742 1379 738 1509 743 1586 730 1627 768 1744 694 1835 653 1906 511 1958 507 2140 556 2237 621 2257 619 2363 287 2363 [[Leuchtenbergia principis]]
poly 621 2363 625 2257 559 2235 510 2137 515 1958 653 1908 767 1744 732 1626 743 1588 739 1516 790 1572 898 1569 907 1817 986 1811 1072 1740 1099 1807 1214 1806 1223 1963 1137 2194 1132 2363 [[Disocactus ackermannii]]
poly 1216 1804 1290 1798 1458 1762 1546 1848 1653 1845 1654 2363 1135 2361 1141 2193 1227 1963 [[Melocactus intortus]]
</imagemap></div>
| image_caption = Various Cactaceae from ''Brockhaus' Konversations-Lexikon v. 2'' 1892
| taxon = Cactaceae
| authority = [[Antoine Laurent de Jussieu|Juss.]]<ref name=APGIII2009/>
| subdivision_ranks = Subfamilies
| subdivision = *[[Cactoideae]]
* [[Maihuenioideae]]
* [[Opuntioideae]]
* [[Pereskioideae]]
* [[Leuenbergerioideae]]

See also [[Classification of the Cactaceae]]
| synonyms = *Opuntiaceae <small>Desv.</small>
* Leuchtenbergiaceae <small>Salm-Dyck ex Pfeiff.</small>
| synonyms_ref = <ref name=gbif.org/>
}}
{{Multiple image |direction=vertical |align=right |width=225|image1=Singapore Botanic Gardens Cactus Garden 2.jpg|image2=Cactus1web.jpg |caption1=Cultivated cacti in the [[Singapore Botanic Gardens]]|caption2=Many species of cactus have long, sharp [[spine (botany)|spines]], like this ''[[Opuntia]]''.}}

A '''cactus''' ({{plural form}}: '''cacti''', '''cactuses''', or less commonly, '''cactus''')<ref name=MerriamWebster/> is a member of the [[plant]] family '''Cactaceae''' ({{IPAc-en|k|æ|k|'|t|eɪ|s|i|.|iː|,_|-|ˌ|aɪ}}),{{efn|group=Note|Although the spellings of botanical families have been largely standardized, there is little agreement among botanists as to how these names are to be pronounced.  The ''{{linktext|-aceae}}'' [[suffix]] can be pronounced {{IPAc-en|ˈ|eɪ|s|i|.|iː}} ({{respell|AY|see|ee}}), {{IPAc-en|ˈ|eɪ|s|i|ˌ|eɪ}} ({{respell|AY|see|ay}}), or {{IPAc-en|ˈ|eɪ|s|iː}} ({{respell|AY|see}}).}} a family of the order [[Caryophyllales]] comprising about 127 genera with some 1,750 known species.<ref name="Christenhusz-Byng2016" /> The word ''cactus'' derives, through Latin, from the [[Ancient Greek]] word {{wikt-lang|grc|κάκτος}} (''káktos''), a name originally used by [[Theophrastus]] for a spiny plant whose identity is now not certain.<ref name=JohnsonSmithStockdalev>{{citation |last1=Johnson |first1=A.T. |last2=Smith |first2=H.A. |last3=Stockdale |first3=A.P. |year=2019 |title=Plant Names Simplified: Their Pronunciation, Derivation & Meaning |page=26 |location=Sheffield, Yorkshire |publisher=5M Publishing |isbn=9781910455067 |name-list-style=amp}}</ref> Cacti occur in a wide range of shapes and sizes. They are native to the Americas, ranging from [[Patagonia]] in the south to parts of western [[Canada]] in the north, with the exception of ''[[Rhipsalis baccifera]]'', which is also found in [[Africa]] and [[Sri Lanka]]. Cacti are adapted to live in very dry environments, including the [[Atacama Desert]], one of the driest places on Earth. Because of this, cacti show many adaptations to conserve water. For example, almost all cacti are [[succulent]]s, meaning they have thickened, fleshy parts adapted to store water. Unlike many other succulents, the stem is the only part of most cacti where this vital process takes place. Most species of cacti have lost true leaves, retaining only [[Thorns, spines, and prickles|spines]], which are highly modified leaves. As well as defending against [[herbivore]]s, spines help prevent water loss by reducing air flow close to the cactus and providing some shade. In the absence of true leaves, cacti's enlarged [[Plant stem|stems]] carry out [[photosynthesis]].

Cactus spines are produced from specialized structures called [[areole]]s, a kind of highly reduced branch. Areoles are an identifying feature of cacti. As well as spines, areoles give rise to [[flower]]s, which are usually tubular and multipetaled. Many cacti have short [[growing season]]s and long dormancies and are able to react quickly to any rainfall, helped by an extensive but relatively shallow root system that quickly absorbs any water reaching the ground surface. Cactus stems are often ribbed or fluted with a number of ribs which corresponds to a number in the [[Fibonacci numbers]] (2, 3, 5, 8, 13, 21, 34 etc.). This  allows them to expand and contract easily for quick water absorption after rain, followed by retention over long [[drought]] periods. Like other succulent plants, most cacti employ a special mechanism called "[[crassulacean acid metabolism]]" (CAM) as part of photosynthesis. [[Transpiration]], during which [[carbon dioxide]] enters the plant and water escapes, does not take place during the day at the same time as photosynthesis, but instead occurs at night. The plant stores the carbon dioxide it takes in as [[malic acid]], retaining it until daylight returns, and only then using it in photosynthesis. Because transpiration takes place during the cooler, more humid night hours, water loss is significantly reduced.

Many smaller cacti have globe-shaped stems, combining the highest possible volume for water storage with the lowest possible surface area for water loss from [[transpiration]]. The tallest{{efn|group=Note|The tallest living cactus is a specimen of ''[[Pachycereus pringlei]]''. The tallest cactus ever measured was an armless [[saguaro]] cactus which blew over in a windstorm in July 1986; it was {{convert|78|ft|m}} tall.<ref name=LAtimes/>}} free-standing cactus is ''[[Pachycereus pringlei]]'', with a maximum recorded height of {{convert|19.2|m|ft|abbr=on}},<ref name=Sala00/> and the smallest is ''[[Blossfeldia liliputiana]]'', only about {{convert|1|cm|in|abbr=on|1}} in diameter at maturity.<ref name=mauseth/> A fully grown saguaro (''[[Carnegiea gigantea]]'') is said to be able to absorb as much as {{convert|200|USgal|l impgal|sp=us}} of water during a rainstorm.<ref name=nps/> A few species differ significantly in appearance from most of the family. At least superficially, plants of the genera ''[[Leuenbergeria]]'', ''[[Rhodocactus]]'' and ''[[Pereskia]]'' resemble other trees and shrubs growing around them. They have persistent leaves, and when older, bark-covered stems. Their areoles identify them as cacti, and in spite of their appearance, they, too, have many adaptations for [[water conservation]]. ''Leuenbergeria'' is considered close to the ancestral species from which all cacti evolved. In tropical regions, other cacti grow as forest climbers and [[epiphyte]]s (plants that grow on trees). Their stems are typically flattened, almost leaf-like in appearance, with fewer or even no spines, such as the well-known Christmas cactus or Thanksgiving cactus (in the genus ''[[Schlumbergera]]'').

Cacti have a variety of uses: many species are used as ornamental plants, others are grown for fodder or forage, and others for food (particularly their fruit). [[Carmine|Cochineal]] is the product of an insect that lives on some cacti.

Many [[succulent plant]]s in both the [[Old World|Old]] and [[New World]] – such as some [[Euphorbiaceae]] (euphorbias) – are also spiny stem succulents and because of this are sometimes incorrectly referred to as "cactus".{{citation needed|date=June 2021}}