Cycadales: diferenças entre revisões
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{{Para|os insectos com nome similar|Cicadidae}} |
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#REDIRECT [[Cicadófita]] |
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{{Info/Taxonomia |
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| nome = Cycadales |
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| fossil_range = {{Período fóssil|Cisuraliano|0|earliest=300|[[Cisuraliano]]–[[Holoceno]]}} |
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| imagem = Cycas circinalis.jpg |
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| imagem_legenda = ''[[Cycas rumphii]]''com [[estróbilo]]s masculinos jovem (erecto) e maduro (pendente). |
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| reino=[[Plantae]] |
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| clado1=[[Tracheophyta]] |
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| clado2=[[Spermatophyta]] |
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| clado3=[[Gymnospermae]] |
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| divisão=[[Cycadophyta]] |
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| divisão_autoridade= [[Charles Edwin Bessey|Bessey]] 1907: 321.<ref name="Bessey 1907">{{cite journal | last=Bessey | first=C.E. | year=1907 | title=A synopsis of plant phyla | journal=Nebraska Univ. Stud. | volume=7 | pages=275–373 }}</ref> |
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| classe=[[Cycadopsida]] |
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| classe_autoridade = [[Adolphe-Théodore Brongniart|Brongn.]]<ref name="Brongniart 1843">{{cite book | last=Brongniart | first=A. | year=1843 | title=Énumération des genres de plantes cultivées au Muséum d'histoire naturelle de Paris }}</ref> |
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| ordem = '''Cycadales''' |
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| ordem_autoridade = [[Pers.]] ''ex'' [[Bercht.]] & [[J.Presl]] |
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| subdivisão_nome = Famílias extantes |
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| subdivisão = |
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*[[Cycadaceae]] |
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*[[Zamiaceae]] |
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| range_map = |
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| range_map_caption = Global distribution of modern cycads |
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| sinónimos = |
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* [[Cycadofilicales]] <small>Němejc 1950</small> |
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* [[Dioales]] <small>Doweld 2001</small> |
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* [[Stangeriales]] <small>Doweld 2001</small> |
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* [[Zamiales]] <small>Burnett 1835</small> |
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}} |
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[[File:Cycads, Limpopo, South Africa (2417726335).jpg|thumb|280px|Cicas na Província do Limpopo, África do Sul.]] |
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[[File: Cycad leaves semicircle.jpg|thumb|280px|As cicas apresentam uma roseta de folhas pinadas em torno de um tronco cilíndrico.]] |
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'''Cycadales''' é uma [[Ordem (biologia)|ordem]] de [[Gymnospermae|plantas com sementes nuas]] ([[Gymnospermae]]) [[perenifólia]]s que normalmente apresentam um [[tronco (botânica)|tronco]] robusto e lenhoso encimado por uma [[coroa (botânica)|coroa]] de grandes folhas, duras e rígidas, geralmente [[pinada]]s, que lhe conferem um aspecto superficialmente semelhante a [[Arecaceae|palmeiras]] ou a [[feto arbóreo|fetos arbóreos]]. As espécies são [[dioica]]s, isto é, com indivíduos que são exclusivamnete masculinos ou femininos. As cicadáceas variam em tamanho, com troncos de apenas alguns centímetros a vários metros de altura. Geralmente crescem muito lentamente<ref>{{Cite journal |last=Dehgan |first=Bijan |year=1983 |title=Propagation and Growth of Cycads—A Conservation Strategy |url=https://journals.flvc.org/fshs/article/view/95611 |journal=Proceedings of the Florida State Horticultural Society |volume=96 |pages=137–139|via=Florida Online Journals}}</ref> e apresentam grande [[longevidade]]. As Cycadales em todo o mundo estão em declínio, com quatro espécies à beira da extinção e sete espécies com menos de 100 plantas na natureza.<ref>{{Cite news |last=Davis |first=Judi |date=2018-06-27 |title=Meet Durban's famous cycad family |work=South Coast Herald |url=https://southcoastherald.co.za/297604/meet-durbans-famous-cycad-family/ |access-date=2022-09-11}}</ref> |
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==Descrição== |
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As Cycadales são [[gimnospermas]] (com sementes nuas), o que significa que as sementes [[fertilização|não fertilizadas]] estão abertas ao ar para serem fertilizadas diretamente por [[polinização]], em contraste com [[angiospermas]], que têm sementes fechadas com arranjos de fertilização mais complexos. As cicadáceas têm [[polinizador]]es muito especializados, geralmente uma espécie específica de [[Coleoptera|coleópteros]]. Tanto as plantas masculinas como as femininas produzem cones ([[estróbilo]]s) um pouco semelhantes às pinhas das [[conífera]]s. |
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Está comprovado que as cicadáceas [[fixação de azoto|fixam azoto atmosférico]] em associação com várias [[cianobactérias]] que vivem nas suas raízes (as [[raiz coraloide|raízes "coraloides"]]).<ref>{{cite journal |vauthors=Rai AN, Soderback E, Bergman B |year=2000 |title=Tansley Review No. 116. Cyanobacterium-Plant Symbioses |journal=The New Phytologist |volume=147 |issue=3 |pages=449–481 |jstor=2588831 |doi=10.1046/j.1469-8137.2000.00720.x |pmid=33862930 |doi-access=free }}</ref> Essas bactérias fotossintéticas produzem uma [[neurotoxina]] designada por [[BMAA]] que é encontrada nas [[semente]]s das cicadáceas. Essa neurotoxina pode entrar na cadeia alimentar humana, pois as sementes das cicadáceas podem ser consumidas diretamente como fonte de farinha por humanos ou por animais selvagens, como os morcegos, ou ferais e os humanos podem comer esses animais. Supõe-se que esta seja a fonte de algumas [[doenças neurológicas]] em humanos.<ref name=Holtcamp>{{cite journal | author = Holtcamp, W. | year = 2012 | title = The emerging science of BMAA: do cyanobacteria contribute to neurodegenerative disease? | journal = Environmental Health Perspectives | volume = 120 | issue = 3 | doi = 10.1289/ehp.120-a110 | pmid=22382274 | pmc=3295368 | pages=a110–a116}}</ref><ref name="Cox and Davis">{{cite journal | vauthors = Cox PA, Davis DA, Mash DC, Metcalf JS, Banack SA | year = 2015 | title = Dietary exposure to an environmental toxin triggers neurofibrillary tangles and amyloid deposits in the brain | journal = Proceedings of the Royal Society B | volume = 283 | issue = 1823 | doi = 10.1098/rspb.2015.2397 | pages=20152397 | pmid=26791617 | pmc=4795023}}</ref> |
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Outro mecanismo de [[Defesa contra a herbivoria|defesa contra herbívoros]] é a acumulação de toxinas nas sementes e nos tecidos vegetativos; através da [[transferência horizontal de genes]], as cicadáceas adquiriram uma família de genes de um organismo microbiano, provavelmente um fungo, que lhes dá a capacidade de produzir uma toxina insecticida.<ref>{{cite journal | doi=10.1038/s41477-022-01129-7 |doi-access=free | title=The Cycas genome and the early evolution of seed plants | year=2022 | last1=Liu | first1=Yang | last2=Wang | first2=Sibo | last3=Li | first3=Linzhou | last4=Yang | first4=Ting | last5=Dong | first5=Shanshan | last6=Wei | first6=Tong | last7=Wu | first7=Shengdan | last8=Liu | first8=Yongbo | last9=Gong | first9=Yiqing | last10=Feng | first10=Xiuyan | last11=Ma | first11=Jianchao | last12=Chang | first12=Guanxiao | last13=Huang | first13=Jinling | last14=Yang | first14=Yong | last15=Wang | first15=Hongli | last16=Liu | first16=Min | last17=Xu | first17=Yan | last18=Liang | first18=Hongping | last19=Yu | first19=Jin | last20=Cai | first20=Yuqing | last21=Zhang | first21=Zhaowu | last22=Fan | first22=Yannan | last23=Mu | first23=Weixue | last24=Sahu | first24=Sunil Kumar | last25=Liu | first25=Shuchun | last26=Lang | first26=Xiaoan | last27=Yang | first27=Leilei | last28=Li | first28=Na | last29=Habib | first29=Sadaf | last30=Yang | first30=Yongqiong | journal=Nature Plants | volume=8 | issue=4 | pages=389–401 | pmid=35437001 | pmc=9023351 | display-authors=1 }}</ref> |
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== Description == |
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Cycads have a [[cylindrical]] trunk which usually does not [[branch]]. However, some types of cycads, such as ''[[Cycas zeylanica]],'' can branch their trunks. The apex of the stem is protected by modified leaves called [[cataphyll]]s.<ref>{{cite journal | pmc=6315973 | year=2018 | last1=Marler | first1=T. E. | last2=Krishnapillai | first2=M. V. | title=Does Plant Size Influence Leaf Elements in an Arborescent Cycad? | journal=Biology | volume=7 | issue=4 | page=51 | doi=10.3390/biology7040051 | pmid=30551676 | doi-access=free }}</ref> Leaves grow directly from the trunk, and typically fall when older, leaving a crown of leaves at the top. The leaves grow in a [[rosette (botany)|rosette]] form, with new foliage emerging from the top and center of the crown. The trunk may be buried, so the leaves appear to be emerging from the ground, so the plant appears to be a [[rosette (botany)|basal rosette]]. The leaves are generally large in proportion to the trunk size, and sometimes even larger than the trunk. |
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The leaves are [[pinnate]] (in the form of bird feathers, [[pinnation|pinnae]]), with a central leaf stalk from which parallel "ribs" emerge from each side of the stalk, perpendicular to it. The leaves are typically either compound (the leaf stalk has [[leaflet (botany)|leaflets]] emerging from it as "ribs"), or have edges ([[Leaf margin|margin]]s) so deeply cut ([[Wiktionary:incised|incised]]) so as to appear compound. The Australian genus [[Bowenia]] and some Asian species of Cycas, like [[Cycas multipinnata]], [[Cycas micholitzii]] and [[Cycas debaoensis]], have leaves that are [[bipinnate]], which means the leaflets each have their own subleaflets, growing in the same form on the leaflet as the leaflets grow on the stalk of the leaf ([[fractal|self-similar geometry]]).<ref>{{Cite book |last=Rutherford |first=Catherine |url=https://www.kew.org/sites/default/files/2019-02/CITESCycadsPack.pdf.pdf |title=CITES and Cycads: A User's Guide |publisher=Royal Botanic Gardens, Kew |display-editors=et al.}}</ref><ref>{{cite book | url=https://books.google.com/books?id=_EMbBAAAQBAJ&dq=C.+multipinnata+within+the+genus.+C.+debaoensis&pg=PA129 | title=Cycadaceae Family | isbn=9781300654537 | last1=Lariushin | first1=Boris | date=19 January 2013 }}</ref> |
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== Confusion with palms == |
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Due to superficial similarities in foliage and plant structure, cycads and [[Arecaceae|palms]] are often mistaken for each other. They also can occur in similar climates. However, they belong to different [[Phylum|phyla]] and as such are not closely related. The similar structure is the product of [[convergent evolution]]. |
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Beyond those superficial resemblances, there are a number of differences between cycads and palms. For one, both male and female cycads are [[gymnosperm]]s and bear cones (strobili), while palms are [[angiosperm]]s and so flower and bear fruit. The mature foliage looks very similar between both groups, but the young emerging leaves of a cycad resemble a [[fiddlehead fern]] before they unfold and take their place in the rosette, while the leaves of palms are just small versions of the mature frond. Another difference is in the [[Plant stem|stem]]. Both plants leave some scars on the stem below the rosette where there used to be leaves, but the scars of a cycad are [[Helical symmetry|helically]] arranged and small, while the scars of palms are a circle that wraps around the whole stem. The stems of cycads are also in general rougher and shorter than those of palms.<ref>{{Cite book |title=The Tree |last=Tudge |first=Colin |publisher=Crown Publishers |year=2006 |isbn=978-1-4000-5036-9 |location=New York |pages=[https://archive.org/details/treenaturalhisto00tudg/page/70 70–72, 139–148] |url-access=registration |url=https://archive.org/details/treenaturalhisto00tudg}}</ref> |
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==Taxonomy== |
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{{More citations needed|date=November 2018}} |
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The two extant [[family (biology)|families]] of cycads all belong to the order [[Cycadales]], and are the [[Cycadaceae]] and [[Zamiaceae]] (including [[Stangeriaceae]]). These cycads have changed little since the Jurassic in comparison to some other plant divisions. Five additional families belonging to the [[Medullosales]] became extinct by the end of the Paleozoic Era. |
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Based on genetic studies, cycads are thought to be more closely related to ''[[Ginkgo]]'' than other living gymnosperms. Both are thought to have diverged from each other during the early [[Carboniferous]].<ref name="Wu 2013">{{cite journal |last1=Wu |first1=Chung-Shien |last2=Chaw |first2=Shu-Miaw |last3=Huang |first3=Ya-Yi |date=January 2013 |title=Chloroplast phylogenomics indicates that ''Ginkgo biloba'' is sister to cycads |journal=Genome Biology and Evolution |volume=5 |issue=1 |pages=243–254 |doi=10.1093/gbe/evt001 |issn=1759-6653 |pmc=3595029 |pmid=23315384 |language=en}}</ref><ref name="Stull 2021">{{cite journal |last1=Stull |first1=Gregory W. |last2=Qu |first2=Xiao-Jian |last3=Parins-Fukuchi |first3=Caroline |last4=Yang |first4=Ying-Ying |last5=Yang |first5=Jun-Bo |last6=Yang |first6=Zhi-Yun |last7=Hu |first7=Yi |last8=Ma |first8=Hong |last9=Soltis |first9=Pamela S. |last10=Soltis |first10=Douglas E. |last11=Li |first11=De-Zhu |date=July 19, 2021 |title=Gene duplications and phylogenomic conflict underlie major pulses of phenotypic evolution in gymnosperms |journal=Nature Plants |volume=7 |issue=8 |pages=1015–1025 |doi=10.1038/s41477-021-00964-4 |pmid=34282286 |s2cid=236141481 |issn=2055-0278 |language=en |url=https://www.nature.com/articles/s41477-021-00964-4}}</ref> |
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{| class="wikitable" |
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|- |
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! colspan=1 | External phylogeny<ref name="Wu 2013"/><ref name="Stull 2021"/> |
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! colspan=1 | Internal phylogeny<ref name="Nagalingum2011">{{cite journal |last1=Nagalingum |first1=N. S. |last2=Marshall |first2=C. R. |last3=Quental |first3=T. B. |last4=Rai |first4=H. S. |last5=Little |first5=D. P. |last6=Mathews |first6=S. |date=2011 |title=Recent synchronous radiation of a living fossil |journal=Science |volume=334 |issue=6057 |pages=796–799 |bibcode=2011Sci...334..796N |doi=10.1126/science.1209926 |pmid=22021670 |s2cid=206535984}}</ref><ref name="Condamine-2015">{{cite journal |last1=Condamine |first1=Fabien L. |last2=Nagalingum |first2=Nathalie S. |last3=Marshall |first3=Charles R. |last4=Morlon |first4=Hélène |date=17 April 2015 |title=Origin and diversification of living cycads: a cautionary tale on the impact of the branching process prior in Bayesian molecular dating |journal=BMC Evolutionary Biology |volume=15 |at=65 |doi=10.1186/s12862-015-0347-8 |pmid=25884423|s2cid=14815027 |language=en |doi-access=free}}</ref> |
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| style="vertical-align:top| |
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{| style="border:0; margin:auto;" |
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|- |
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|style="padding:10px;"|{{clade |
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|1={{clade |
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|1='''Cycads''' |
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|2=''[[Ginkgo]]'' |
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|3={{clade |
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|1=[[Conifers]] |
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|label2=Anthophytes |
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|2={{clade |
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|1=[[Bennettitales]] |
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|2=[[Gnetales]] |
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|3=[[Angiosperms]] |
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}} |
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}} |
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}} |
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}} |
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|style="padding:10px;"|{{clade |
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|1={{clade |
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|label1=[[Gymnosperm]]s |
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|1={{clade |
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|1='''Cycads''' |
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|2=''[[Ginkgo]]'' |
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|3={{clade |
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|1=[[Conifers]] |
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|2=[[Gnetophytes]] |
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}} |
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}} |
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|label2=[[Angiosperm]]s |
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|2=(flowering plants) |
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}} |
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}} |
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|- |
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!<br/>{{small|Traditional view}} |
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!<br/>{{small|Modern view}} |
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|} |
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| |
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{{clade|style=font-size:90%;line-height:80%;width:300px |
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|label1 =Cycads |
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|1={{clade |
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|label1=Cycadineae |
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|1={{clade |
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|label1=[[Cycadaceae]] |
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|1=''[[Cycas]]'' |
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}} |
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|label2=Zamiineae |
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|2={{clade |
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|label1=[[Zamiaceae]] |
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|1={{clade |
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|label1=Diooideae |
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|1=''[[Dioon]]'' |
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|label2=Zamioideae |
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|2={{clade |
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|label1=Encephalarteae |
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|1={{clade |
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|1=''[[Macrozamia]]'' |
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|2={{clade |
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|1=''[[Lepidozamia]]'' |
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|2=''[[Encephalartos]]'' |
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}} |
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}} |
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|label2=Zamieae |
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|2={{clade |
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|1=''[[Bowenia]]'' |
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|2={{clade |
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|1={{clade |
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|1=''[[Ceratozamia]]'' |
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|2=''[[Stangeria]]'' |
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}} |
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|2={{clade |
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|1=''[[Zamia]]'' |
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|2=''[[Microcycas]]'' |
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}} |
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}} |
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}} |
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}} |
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}} |
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}} |
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}} |
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}} |
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|} |
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Classification of the Cycadophyta to the rank of family. |
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* Class Cycadopsida <small>Brongniart 1843</small> |
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** Order Cycadales <small>Persoon ex von Berchtold & Presl 1820</small> |
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*** Suborder Cycadineae <small>Stevenson 1992</small> |
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**** Family [[Cycadaceae]] <small>Persoon 1807</small> |
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***** Genus ''[[Cycas]]'' |
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*** Suborder Zamiineae <small>Stevenson 1992</small> |
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**** Family [[Zamiaceae]] <small>Horaninow 1834</small> |
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***** subfamily Diooideae <small>Pilg. 1926</small> |
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****** Tribe Diooeae <small>Schuster</small> |
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******* Genus ''[[Dioon]]'' |
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***** subfamily Zamioideae <small>Stevenson 1992</small> |
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****** Tribe Encephalarteae <small>Miquel 1861</small> |
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******* Genus ''[[Macrozamia]]'' |
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******* Genus ''[[Lepidozamia]]'' |
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******* Genus ''[[Encephalartos]]'' |
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****** Tribe Zamieae <small>Miquel 1861</small> |
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******* Genus ''[[Bowenia]]'' |
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******* Genus ''[[Ceratozamia]]'' |
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******* Genus ''[[Stangeria]]'' |
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******* Genus ''[[Zamia]]'' |
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******* Genus ''[[Microcycas]]'' |
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Extinct cycad genera: |
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* ''[[Antarcticycas]]'' Middle Triassic, Antarctica (known from the whole plant)<ref>{{Cite journal |last1=Hermsen |first1=Elizabeth J. |last2=Taylor |first2=Edith L. |last3=Taylor |first3=Thomas N. |date=January 2009 |title=Morphology and ecology of the ''Antarcticycas'' plant |journal=Review of Palaeobotany and Palynology |language=en |volume=153 |issue=1–2 |pages=108–123 |doi=10.1016/j.revpalbo.2008.07.005}}</ref> |
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* ''[[Ctenis]]'' Mesozoic-Paleogene, Worldwide (leaf form genus) |
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* ''[[Pseudoctenis]]'' (leaf form genus) |
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==Fossil record== |
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[[File:Bowenia spectabilis.JPG|thumb|''[[Bowenia spectabilis]]'' : plant with single frond in the Daintree rainforest, north-east Queensland]] |
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[[File:Cycad cone.jpg|right|thumb|Leaves and strobilus of ''[[Encephalartos sclavoi]]'']] |
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The oldest probable cycad foliage is known from the latest Carboniferous-Early Permian of South Korea and China, such as ''[[Crossozamia]]''. Unambiguous fossils of cycads are known from the Early-Middle Permian onwards.<ref>{{Cite journal |last1=Spiekermann |first1=Rafael |last2=Jasper |first2=André |last3=Siegloch |first3=Anelise Marta |last4=Guerra-Sommer |first4=Margot |last5=Uhl |first5=Dieter |date=June 2021 |title=Not a lycopsid but a cycad-like plant: ''Iratinia australis'' gen. nov. et sp. nov. from the Irati Formation, Kungurian of the Paraná Basin, Brazil |journal=Review of Palaeobotany and Palynology |language=en |volume=289 |pages=104415 |doi=10.1016/j.revpalbo.2021.104415 |s2cid=233860955}}</ref> Cycads were generally uncommon during the Permian.<ref>{{Cite journal |last=Gomankov |first=A. V. |date=June 2022 |title=Cycads in the Permian of thе Subangara Region |journal=Paleontological Journal |language=en |volume=56 |issue=3 |pages=317–326 |doi=10.1134/S0031030122030066 |s2cid=249627815 |issn=0031-0301}}</ref> The two living cycad families are thought to have split from each other sometime between the Jurassic<ref name="Nagalingum2011" /> and Carboniferous.<ref name=":0">{{Cite journal |last=Coiro |first=Mario |last2=Allio |first2=Rémi |last3=Mazet |first3=Nathan |last4=Seyfullah |first4=Leyla J. |last5=Condamine |first5=Fabien L. |date=2023-06-11 |title=Reconciling fossils with phylogenies reveals the origin and macroevolutionary processes explaining the global cycad biodiversity |url=https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.19010 |journal=New Phytologist |language=en |doi=10.1111/nph.19010 |issn=0028-646X}}</ref> Cycads reached their apex of diversity during the Mesozoic. Although the Mesozoic is sometimes called the "Age of Cycads," the foliage of cycads is very similar to other groups of extinct seed plants, such as [[Bennettitales]] and [[Nilssonia (plant)|Nilssoniales]], that are not closely related, and cycads were probably only a minor component of mid-Mesozoic floras, with Bennettitales and Nilsonniales being more abundant than cycads.<ref name="Coiro-2017">{{Cite journal |last1=Coiro |first1=Mario |last2=Pott |first2=Christian |date=December 2017 |title=Eobowenia gen. nov. from the Early Cretaceous of Patagonia: indication for an early divergence of Bowenia? |journal=BMC Evolutionary Biology |language=en |volume=17 |issue=1 |pages=97 |doi=10.1186/s12862-017-0943-x |issn=1471-2148 |pmc=5383990 |pmid=28388891}}</ref> The oldest records of the modern genus ''Cycas'' are from the Paleogene of East Asia.<ref>{{Cite journal |last1=Liu |first1=Jian |last2=Lindstrom |first2=Anders J |last3=Marler |first3=Thomas E |last4=Gong |first4=Xun |date=2022-01-28 |title=Not that young: combining plastid phylogenomic, plate tectonic and fossil evidence indicates a Palaeogene diversification of Cycadaceae |journal=Annals of Botany |language=en |volume=129 |issue=2 |pages=217–230 |doi=10.1093/aob/mcab118 |doi-access=free |issn=0305-7364 |pmc=8796677 |pmid=34520529}}</ref> Fossils assignable to Zamiaceae are known from the Cretaceous,<ref name="Coiro-2017" /> with fossils assignable to living genera of the family known from the Cenozoic.<ref name="Condamine-2015" /> |
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[[File:Fossilized cycad New York Botanical Garden.jpg|thumb|Petrified cycad fossil, New York Botanical Garden]] |
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==Distribution== |
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{{see also|List of cycad species by country}} |
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The living cycads are found across much of the [[subtropical]] and [[tropical]] parts of the world, with a few in temperate regions such as in Australia.<ref name="Orchard1998">Orchard, A.E. & McCarthy, P.M. (eds.) (1998). Flora of Australia 48: 1-766. Australian Government Publishing Service, Canberra.</ref> The greatest diversity occurs in [[South America|South]] and [[Central America]].{{citation needed|date=July 2015}} They are also found in [[Mexico]], the [[Antilles]], southeastern [[United States of America|United States]], [[Australia]], [[Melanesia]], [[Micronesia]], [[Japan]], [[China]], [[Southeast Asia]], [[Bangladesh]], [[India]], [[Sri Lanka]], [[Madagascar]], and [[Southern Africa|southern]] and tropical [[Africa]], where at least 65 [[species]] occur. Some can survive in harsh [[desert]] or semi-desert [[climate]]s ([[xerophytic]]),<ref>{{cite report |title=National Recovery Plan for the MacDonnell Ranges Cycad ''Macrozamia macdonnellii'' |publisher=Department of Natural Resources, Environment, The Arts and Sport, Northern Territory |url=http://www.environment.gov.au/system/files/resources/c17de516-c635-4c67-b040-c9db4da380e4/files/macrozamia-macdonnellii.pdf |access-date=16 July 2015}}</ref> others in wet [[rain forest]] conditions,<ref>{{cite book |author1=Bermingham, E. |author2=Dick, C.W. |author3=Moritz, C. |year=2005 |title=Tropical Rainforests: Past, Present, and Future |publisher=University of Chicago Press |isbn=9780226044682 |url=https://books.google.com/books?id=Y3dXZyCCDpEC}}</ref> and some in both.<ref>{{citation |chapter-url=http://iucnredlist.org/details/42000/0 |title=The IUCN Red List of Threatened Species |chapter=''Macrozamia communis''}}</ref> Some can grow in [[sand]] or even on [[rock (geology)|rock]], some in oxygen-poor, swampy, [[bog]]-like soils rich in [[organic material]].{{Citation needed|date=April 2011}} Some are able to grow in full sun, some in full shade, and some in both.{{Citation needed|date=April 2011}} Some are [[Sodium chloride|salt]] tolerant ([[halophyte]]s).{{citation needed|date=July 2015}} |
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Species diversity of the extant cycads peaks at 17˚ 15"N and 28˚ 12"S, with a minor peak at the [[equator]]. There is therefore not a [[Latitudinal gradients in species diversity|latitudinal diversity gradient]] towards the equator but towards the [[Tropic of Cancer]] and the [[Tropic of Capricorn]]. However, the peak near the northern tropic is largely due to ''Cycas'' in Asia and ''Zamia'' in the New World, whereas the peak near the southern tropic is due to ''Cycas'' again, and also to the diverse genus ''Encephalartos'' in southern and central Africa, and ''Macrozamia'' in Australia. Thus, the distribution pattern of cycad species with latitude appears to be an artifact of the geographical isolation of the remaining cycad genera and their species, and perhaps because they are partly [[xerophytic]] rather than simply [[tropical]].{{efn|The distribution area on the map should be expanded to include the range of ''Macrozamia macdonnelliana'' in the central region of Australia, ''Zamia boliviana'' in Bolivia and Mato Grosso, Brazil, ''Cycas thouarsii'' on Comoros and Seychelles, and ''Cycas micronesica'' on the islands of Guam, Palau, Rota, & Yap.}}{{efn|Also, the depiction of cycad distribution in Africa, particularly the western boundary, should be improved to show the actual range limits, rather than national borders.}} |
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==Etnobotânica== |
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Em [[Vanuatu]], as cicadáceas são conhecidas como ''[[namele]]'' e são um importante símbolo da cultura tradicional. Servem como um poderoso sinal de [[tabu]],<ref>{{cite web |author=Dan McGarry |date=Apr 9, 2018 |title=A Princely Title |website=Vanuatu Daily Post |url=http://dailypost.vu/news/a-princely-title/article_3b08dcb8-6286-51f6-bc85-ac5aee546242.html}}</ref> e um par de folhas de ''namele'' aparecem na [[Bandeira de Vanuatu|bandeira nacional]] e na [[brasão|heráldica]] daquele país. Juntamente com a espécie ''[[Cordyline terminalis]]'', conhecida como ''[[nanggaria]]'', outro símbolo da cultura de Vanuatu, o ''namele'' também dá nome ao [[Nagriamel]], um movimento político daquele país. |
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==Notas== |
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{{notelist}} |
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==Referências== |
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{{reflist|25em}} |
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==Ver também== |
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*[[Fossil Cycad National Monument]], um sítio de interesse geológico no estado de [[South Dakota]]. |
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=={{Links}}== |
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{{Commons|Cycadophyta}} |
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* {{cite web |url=http://palm-trees.org/ |title=Palm Trees, Small Palms, Cycads, Bromeliads and tropical plants |archive-url=https://web.archive.org/web/20140520003137/http://palm-trees.org/ |archive-date=2014-05-20}} Site with thousands of large, high quality photos of cycads and associated flora. Includes information on habitat and cultivation. (Site is dead.) |
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* {{cite web |title=The Cycad Pages |publisher=Royal Botanic Gardens Sydney |url= http://plantnet.rbgsyd.nsw.gov.au/PlantNet/cycad/index.html |archive-date=29 Março 2021 |archive-url=https://web.archive.org/web/20210329132148/https://plantnet.rbgsyd.nsw.gov.au/PlantNet/cycad/index.html}} |
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* {{cite web |url=http://www.conifers.org/zz/cycadales.htm |title=Gymnosperm Database: Cycads |archive-url=https://web.archive.org/web/20100810215325/http://www.conifers.org/zz/cycadales.htm |archive-date=2010-08-10}} |
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* {{cite web |title=Fairchild Tropical Botanic Garden |url=http://www.fairchildgarden.org/horticulture/n_collections.html |archive-url=https://web.archive.org/web/20150223092247/http://www.fairchildgarden.org/horticulture/n_collections.html |archive-date=2015-02-23}} One of the largest collections of cycads in the world in Florida, U.S.A. |
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* {{cite web |title=Main Page |url=http://www.pacsoa.org.au/ |publisher=Palm and Cycad Societies of Australia (PACSOA) |access-date=2023-06-18}} |
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* {{cite web |title=Welcome |url=http://cycadsociety.org/ |publisher=The Cycad Society of South Africa |access-date=2023-06-18}} |
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* {{cite web |author=David Dalton |date=1997 |title=Part I. The range of organisms that can fix nitrogen |website=Nitrogen Fixation |url=http://academic.reed.edu/biology/Nitrogen/Nfix1.html |access-date=2023-06-18}} Cycad nitrogen fixation |
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* {{cite web |title=Cycad toxicity |website=The Cycad Pages |publisher=Royal Botanic Gardens Sydney |url=http://plantnet.rbgsyd.nsw.gov.au/PlantNet/cycad/toxic.html |archive-date=2020-07-17 |archive-url=http://web.archive.org/web/20200717151457/http://plantnet.rbgsyd.nsw.gov.au/PlantNet/cycad/toxic.html}} |
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* {{cite web |author=Lauren Kessler |date=28 de agosto de 2005 |url=https://www.nytimes.com/2005/08/28/magazine/the-cult-of-the-cycads.html |archive-url=http://web.archive.org/web/20220604003638/https://www.nytimes.com/2005/08/28/magazine/the-cult-of-the-cycads.html |archive-date=2022-06-04 |title=The Cult of the Cycads |work=[[The New York Times Magazine]]}} Magazine article on cycad collectorship and cycad smuggling. |
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{{Taxonbar|from1=Q1089795|from2=Q157114|from3=Q5197912|from4=Q5605610}} |
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{{Acrogymnospermae}} |
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{{Classificação Plantas}} |
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{{Vida na Terra}} |
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[[Categoria:Cycadophyta| ]] |
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Revisão das 17h28min de 26 de julho de 2023
Nota: Para os insectos com nome similar, veja Cicadidae.| Cycadales | |||||||||||||||
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Cycadales é uma ordem de plantas com sementes nuas (Gymnospermae) perenifólias que normalmente apresentam um tronco robusto e lenhoso encimado por uma coroa de grandes folhas, duras e rígidas, geralmente pinadas, que lhe conferem um aspecto superficialmente semelhante a palmeiras ou a fetos arbóreos. As espécies são dioicas, isto é, com indivíduos que são exclusivamnete masculinos ou femininos. As cicadáceas variam em tamanho, com troncos de apenas alguns centímetros a vários metros de altura. Geralmente crescem muito lentamente[3] e apresentam grande longevidade. As Cycadales em todo o mundo estão em declínio, com quatro espécies à beira da extinção e sete espécies com menos de 100 plantas na natureza.[4]
Descrição
As Cycadales são gimnospermas (com sementes nuas), o que significa que as sementes não fertilizadas estão abertas ao ar para serem fertilizadas diretamente por polinização, em contraste com angiospermas, que têm sementes fechadas com arranjos de fertilização mais complexos. As cicadáceas têm polinizadores muito especializados, geralmente uma espécie específica de coleópteros. Tanto as plantas masculinas como as femininas produzem cones (estróbilos) um pouco semelhantes às pinhas das coníferas.
Está comprovado que as cicadáceas fixam azoto atmosférico em associação com várias cianobactérias que vivem nas suas raízes (as raízes "coraloides").[5] Essas bactérias fotossintéticas produzem uma neurotoxina designada por BMAA que é encontrada nas sementes das cicadáceas. Essa neurotoxina pode entrar na cadeia alimentar humana, pois as sementes das cicadáceas podem ser consumidas diretamente como fonte de farinha por humanos ou por animais selvagens, como os morcegos, ou ferais e os humanos podem comer esses animais. Supõe-se que esta seja a fonte de algumas doenças neurológicas em humanos.[6][7]
Outro mecanismo de defesa contra herbívoros é a acumulação de toxinas nas sementes e nos tecidos vegetativos; através da transferência horizontal de genes, as cicadáceas adquiriram uma família de genes de um organismo microbiano, provavelmente um fungo, que lhes dá a capacidade de produzir uma toxina insecticida.[8]
Etnobotânica
Em Vanuatu, as cicadáceas são conhecidas como namele e são um importante símbolo da cultura tradicional. Servem como um poderoso sinal de tabu,[9] e um par de folhas de namele aparecem na bandeira nacional e na heráldica daquele país. Juntamente com a espécie Cordyline terminalis, conhecida como nanggaria, outro símbolo da cultura de Vanuatu, o namele também dá nome ao Nagriamel, um movimento político daquele país.
Notas
Referências
- ↑ Bessey, C.E. (1907). «A synopsis of plant phyla». Nebraska Univ. Stud. 7: 275–373
- ↑ Brongniart, A. (1843). Énumération des genres de plantes cultivées au Muséum d'histoire naturelle de Paris. [S.l.: s.n.]
- ↑ Dehgan, Bijan (1983). «Propagation and Growth of Cycads—A Conservation Strategy». Proceedings of the Florida State Horticultural Society. 96: 137–139 – via Florida Online Journals
- ↑ Davis, Judi (27 de junho de 2018). «Meet Durban's famous cycad family». South Coast Herald. Consultado em 11 de setembro de 2022
- ↑ Rai AN, Soderback E, Bergman B (2000). «Tansley Review No. 116. Cyanobacterium-Plant Symbioses». The New Phytologist. 147 (3): 449–481. JSTOR 2588831. PMID 33862930. doi:10.1046/j.1469-8137.2000.00720.x
- ↑ Holtcamp, W. (2012). «The emerging science of BMAA: do cyanobacteria contribute to neurodegenerative disease?». Environmental Health Perspectives. 120 (3): a110–a116. PMC 3295368. PMID 22382274. doi:10.1289/ehp.120-a110
- ↑ Cox PA, Davis DA, Mash DC, Metcalf JS, Banack SA (2015). «Dietary exposure to an environmental toxin triggers neurofibrillary tangles and amyloid deposits in the brain». Proceedings of the Royal Society B. 283 (1823). 20152397 páginas. PMC 4795023. PMID 26791617. doi:10.1098/rspb.2015.2397
- ↑ Liu, Yang; et al. (2022). «The Cycas genome and the early evolution of seed plants». Nature Plants. 8 (4): 389–401. PMC 9023351. PMID 35437001. doi:10.1038/s41477-022-01129-7
- ↑ Dan McGarry (Apr 9, 2018). «A Princely Title». Vanuatu Daily Post Verifique data em:
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Ver também
- Fossil Cycad National Monument, um sítio de interesse geológico no estado de South Dakota.
Ligações externas
- «Palm Trees, Small Palms, Cycads, Bromeliads and tropical plants». Cópia arquivada em 20 de maio de 2014 Site with thousands of large, high quality photos of cycads and associated flora. Includes information on habitat and cultivation. (Site is dead.)
- «The Cycad Pages». Royal Botanic Gardens Sydney. Cópia arquivada em 29 Março 2021
- «Gymnosperm Database: Cycads». Cópia arquivada em 10 de agosto de 2010
- «Fairchild Tropical Botanic Garden». Cópia arquivada em 23 de fevereiro de 2015 One of the largest collections of cycads in the world in Florida, U.S.A.
- «Main Page». Palm and Cycad Societies of Australia (PACSOA). Consultado em 18 de junho de 2023
- «Welcome». The Cycad Society of South Africa. Consultado em 18 de junho de 2023
- David Dalton (1997). «Part I. The range of organisms that can fix nitrogen». Nitrogen Fixation. Consultado em 18 de junho de 2023 Cycad nitrogen fixation
- «Cycad toxicity». The Cycad Pages. Royal Botanic Gardens Sydney. Cópia arquivada em 17 de julho de 2020
- Lauren Kessler (28 de agosto de 2005). «The Cult of the Cycads». The New York Times Magazine. Cópia arquivada em 4 de junho de 2022 Magazine article on cycad collectorship and cycad smuggling.