Lesi yi-Welwitschia, isitshalo sasogwadule "esingafi"

E-Afrika sithola enye yezindawo zokuqala ezaqala ukugcina impilo yasemhlabeni: ugwadule lwaseNamib. Yindala ngoba kuyaziwa ukuthi yayivele yakhiwa ngesikhathi se-Tertiary Era, cishe eminyakeni eyizigidi ezingama-65 edlule. Itholakala eningizimu yezwekazi, inendawo engamakhilomitha-skwele ayizinkulungwane ezingama-81. Lapha, kulula ukuthi amazinga okushisa afinyelele kuma-50ºC ehlobo futhi akunakuthinta ezindaweni eziningi, futhi kulapho lapho sithola khona esinye sezitshalo ezingamelana kakhulu emhlabeni: I-Welwitschia mirabilis, okuwukuphela kohlobo lohlobo lwe-Welwitschia.

Abanye bakubiza ngokuthi isitshalo esingafi, noma isitshalo esingafi. Ikhula ngezinga eliphansi kakhulu, kepha ujwayelene kahle nendawo yakhe yokuhlala ukuthi ubehlale efuna ukwazi ukuthi yini imfihlo yakhe. Manje, ekugcineni, ucwaningo lwesayensi lukuvezile.

Ngemvula engamasentimitha amabili kuphela ngonyaka, I-Welwitschia Kuyisitshalo esikhula ngesivinini esikhululekile, kepha lokho akusivimbeli ekubeni siphile iminyaka efinyelela ku-3000, okuyiminyaka elinganiselwa kwezinye zezinhlobo ezithile. Lokhu kusho ukuthi imbewu yahluma ekuqaleni kwe-Iron Age, lapho thina bantu sangafunda hhayi kuphela ukuthi sisebenza kanjani i-ayoni kepha nokuthi sizitshala kanjani izitshalo. Kepha masingaphambuki.

I-Welwitschia yatholwa ngo-1860, ngusosayensi wezitshalo uFriedrich Welwitsch, ngenxa yalesi sizathu, abazange banqikaze ukusebenzisa isibongo sakhe njengegama lohlobo lwesitshalo. Kamuva, uCharles Darwin, kanye nabanye ososayensi, bakhombise intshisekelo yabo kuyo, futhi ikakhulukazi, empilweni yayo ende. Yini eyenza ukuthi ukwazi ukuthi uphile iminyaka engaka ngaphandle kokucwayiza, ngaphansi kwelanga elishisayo nangamaconsi emvula ambalwa ngonyaka?

Izakhi zofuzo ezingajwayelekile zeWelwitschia

Imvamisa, lapho isitshalo sicindezelwa kanjalo siyoma nje, kepha iWelwitschia ayenzi. Siyini isizathu? Iphutha ekuhlukanisweni kwamaseli, okwenzeka eminyakeni engaba yizigidi ezingama-86 edlule. Leli "phutha" lenze ukuthi ufuzo lwesitshalo luphindwe kabili. Kepha akupheleli lapho, ngoba ukuba nezinto eziningi zofuzo kusho ukuthi kufanele usebenzise amandla amaningi, futhi lokhu ehlane cishe kungumsebenzi wokuzibulala, uma kubhekwa izimo zezulu.

Kodwa-ke, i-Welwitschia yayikwazi ukuzivumelanisa nezimo ngaphandle kwezinkinga. Ngokwesifundo, cishe eminyakeni eyizigidi ezimbili edlule umsebenzi wama-retrotransposons (ukusiqonda: yizinto ezingakhuliswa ku-genome) ziqiniswe njengempendulo ekucindezelekeni kokushisa. Lokhu kudale ukuthi kube nezinguquko ezakhiweni zofuzo kepha ngaphandle kokushintsha ukulandelana kwe-DNA okuthulise lawa ma-retrotransposons.

Lezi zinguquko, eyaziwa ngegama lobuchwepheshe le-epigenetics, zidluliselwa zisuka kwesinye isizukulwane ziye kwesinye, ngalo, inzalo yalelo Welwitschia lokuqala elakwazi ukuguquka ukuze lihambisane nogwadule lwaseNamib lase livele selimile ngale mfanelo.

Izintshisakalo I-Welwitschia mirabilis

Ngenxa yalolu shintsho olubalulekile umthamo wesitshalo wehliswa, futhi ngenxa yalokho futhi ukusetshenziswa kwamandla. Kepha kusekhona okunye: amaqabunga ahluma kusuka ku-basal meristem, okungukuthi, evela enkabeni yesitshalo, kanti ezinhlotsheni eziningi amahlamvu amasha avela emagatsheni noma ezihlokweni.

Elinye iqiniso elithakazelisayo ukuthi inamaqabunga amabili kuphela. Uma ubona izithombe kunikeza umuzwa wokuthi kufanele ube nokuningi, kepha empeleni akunjalo. Baqala ngokuba cotyledons cishe ngamamilimitha angama-30, futhi kancane kancane aguqulwa abe amaqabunga alula, aqoshiwe naluhlaza alinganisa cishe imitha elilodwa ngobude.

Yize isomiso singumphikisi ongenakuphikiswa weNamib, lesi sitshalo uyakwazi ukuhlala unamanzi amaningi ngenxa yamazolo akusihlwa. Sijwayele ukucabanga ukuthi izitshalo zimunca amanzi ngezimpande zazo kuphela, kepha imvelaphi enkulu yakho konke esikubonayo nesikwaziyo kusolwandle. Ngakho-ke, ama-pores noma ama-stomata asabela ngokuvula. Uma lina kakhulu, ngakolunye uhlangothi, ziyagcinwa zivaliwe ngoba ukweqisa kwamanzi kungazicwilisa.

Kunzima ngomuntu ukubona iWelwitschia ichuma; noma kunjalo, abanye abanenhlanhla banakho. Ngenxa yabo, kuyaziwa ukuthi uhlobo lwe-dioecious; leyo kukhona izinhlobo zesilisa nezinye zesifazane. Lokhu kuhlanganisa kuphela amathuba okushiya inzalo, yingakho cishe kungenakwenzeka ukuthola imbewu ezothengiswa, futhi uma itholakala, inenani eliphakeme (ngasendleleni, uma uyithola, ungakhohlwa ukuyiphatha impuphu yethusi njengoba zisengozini yokutheleleka ngezifo).

Izimbali ziqoqwe kuma-inflorescence aqhuma enkabeni yesitshalo, futhi zibomvu. Azinawo amacembe, njengoba lezi kuyizakhiwo ezisendaweni efana nogwadule, lapho kungekho zinambuzane, ezingabiza inani elikhulu lamanzi hhayi nhlobo.

Ngakho-ke, i I-Welwitschia mirabilis kungasiza izazi zezitshalo ukuthuthukisa izitshalo ezingamelana kakhulu nezindawo ezomile, into ezosiza uma sinaka ukuthi ezingxenyeni eziningi zomhlaba isimo sezulu siyafudumala futhi amafu emvula abonakala encipha.

Lesi isixhumanisi sokutadisha uma kwenzeka unentshisekelo: Ukutadisha kwemvelo