Sex Change in Cycads

Home , Cycas, Cycas thouarsii

Palms& CycadsNo 76 July - September2002 1 Sex Change in Cycads Rov Osbornet and Root Gorelick2 tP O Box 244, Burpengary, Queensland,4505Australia :Department of Biology, Arizona State University, Tbmpe,AZ 85287-1501, U.S.A.

Introduction Trees", also mentionstwo cycad sex changeincidents: a fernalespecirnen of Becausecycads are strictly and Cycascircinalis fagain,rlore probably C. unifonnly dioecious,occasional early rumphiil that changedto male after being reportsof sex changein theseplants were mechanicallydarnaged fthis rnay be the largely discountedas erroneous(Mehra samecase as referredto by Charnberlain]. 1986).lndeed, there have been some claims and a male of the salnespecies which of sexchanges for which otherexplanations produceda fernalecone after severefrost are rrore appropriate.Nevertheless, exposure. attentionmust be paid to the increasing A detailedaccount of a particularcycad numberof apparentlygenuine cases of sex sex reversalis given by Van Wyk & changesthat have been reportedover the Claassen( l98l) andrelates to oneof several past70 years.In this articlewe sutnmarise specirnens of Encephalartos incidentsof 30 cycad sex reversals, umbeluziensisgrowing in Dr Claassen's including several previously un- garden in Pretoria, South Africa. The documentedcases. We alsomention details particularspecimen produced a malecone of some"false" cases and suggest possible in 1970,but a fernalecone in l9l9 and controlling mechanisms. A table thereafter.As theplant in questionwas in a summarisesthe known casesof cycad sex rlore exposedsituation that others in the change,and a bibliographyis provided. salnegarden, it is speculatedthat a freak cold weatherspell in 1972may haveinitiated Know,n cases o.f'sex change - listed the change. chronologicalllt "Encephalartos",the journal of the Cycad Society of South Africa, has The earliestreference to sex changein publicisednurlerous incidents of cycadsex cycadsis that given by Schuster(1932) change.These are summarised in this and who tells of a Cvc'asrevoluta plant that the following paragraph.H.J. "Maans" was longitudinallybisected fone wonders Kernp( 1985)reporled ona Cycasrevoluta, why!], the two halvesgoing to separate growing in a South African gardenthat places.Happily, both sections survived, but changedfrorn male to fernaleafter being provedto be of oppositegender. Charles transplanted.A fernaleZamia plant was Charnberlain( 1935) tells oflwo sexreversals: saidto haveproduced a sidebranch bearing a cultivated plant of Cycas revoluta tn a male cone(Osborne 1985). A plant of Australia which changedfrom fernaleto Enc'ephalartoslati.fi'orts, transplanted in rnale,and a bud frorn a fernalespecimen of 1970to a fann near East London, South C),r'nt c'ir"cinalisIrnore probably C. Africa, boretwo successivecrops of fernale runtphiif from a Chicago conservatory coneswith viable seedsbut, following a 16which eventuallyconed as a male. severedrought at theend of 1983, produced Menninger(1967), in his book "Fantastic male conesfor the two yearsfollowing tlzanbsDA DtutDZ 'se^?el 'auJoqso ,(o6 :otoq4 aql lsSuoure pedde;1 II el€tu6l Jo r{cleqeJo rnoc ururueJ:ea,{ snotnerd eqt tuou speasJo Jeqtunua8rel u alrq,tr 'GeOt seuoo elpru xrs saIJJEJxedu uals eqJ 'eJIUV qlnos 'ueqJnCIul euroqso)euoc eletu 'fl31l uepre8 etenrrd e ur srsuaZtnqlapplw sutnloqdaruE go uarutceds e pe3npoJd.rue,,(euo e ur a8ueqc xes elelu ol elELueJe Jo ecuopt^g :aôqr 1 a.rn81g 'eoueg ur uopJe8eleAIJd e ur 8uLry\oJBDrulotat sm{J eletueJV'(tq8ulernAIC ees)(1661 euroqso) seuoc oletuxrs pecnpoJdJeei{ euo 'speas Jo sdoJcJelnBeJ 8urnr8' srsuaS.tnqppplut sot"tDI0qda)ug Jo ueturceds el€rueJumo;8 uep.re8y '(000t euroqsg)IIB t€ euoc lou plp prlqt eql elrq^\ s:ee.(enrssoccns eeJql JoJ seuoc eletu pecnpo.rdeuo 'al€lueJe se peuoc euo 'perolruoru flluenbesqns eJeA\ OeJql pu€ peqsrlqelse-er'peAotueJ ere/KeseqJ'fllureqdr-red sJelcns ouru pecnpo.rd 'sdorc paes elqer^ qlr^{ seuocpecnpord fpeln8er peqr{crq^{'[uode; luur8uo oql ul stsuaoqwoqat'g) snso)uuas'Egouaurceds eleureJ eJnl?tu v '(OOOteuroqsg) souoc ole\u e^?ts 9861 reue 1nq Surlueldsuu-r1 '(SOOt 'euoc eue.(ruo1)euoc rege LL6I ur pegoqe qrrq^\ e eletu e Suueeq qcuerq I€relel e pecnpo.rd pecnpord'speeselqerl qlrl\ euoceletual e uedel ur Dtnloâ"t socr(3 eletueJ plo eroqVL6l ur qcrq^\ 'snsolpasoL,rnloqdacug '(SOO1 '(OOO me(-gpe',t11eurg due>lueelg)gueld eleureJ ernletu V 1 euroqsg) Surcnpord-euocelerual olur pedoloâp el?tu ot eletuoJ ruo4 porelle f,ypesoddns 'suorlrpuoc [troder 1eut8t-toeql uI stsuaoqwoqal ,fup ,(pelncrged o1 pelcefqns 'gl 'snso71ta. snsoc!ruasso1toloqdarug Jo lueyd so1,toloqdalugJo ueturceds '(686I eletu u^{oDI3 ruo+ peôueJ sJelcns oA\J V snour,(uouy)euoc eletu e qlr^\ 'GOAI euroqso) uepre8eqt ur elrsrerpeqs u1(oJceprs € pecnpord;uef euo 'eleueg e ol pelueldsue-r1Sureq rege selerrralolul e se sree.{Ierales roJ peuoc peq r{crq^\ 'eclrgy 'euo1er4 petlJruBclJJv qtnos ur uopr?c l?cruelog qlnos ur 1ue1dsndot,ta '(SSO1 IeuorlsN pla^,,Ko-Ieql le sueurceds ot.ra8uolgurvror8 pees V euroqs6) One of the particularly interesting sex but a female conethe following year. changeincidents involves a set of l2mature male Cycastaitungensls plants, which were Case 4: Alexandre Viossant Qters. purchasedin July 1997from an Australian comm.)lives on Mayotte Island, one of the nursery for a landscaping project at Comores, where Cycas thouarsii grows BrisbaneInternational Airport. The nursery naturally. A seedling of this species was was selectively selling off surplus male planted next to the Viossant family home plantswhile keepingfemale plants for seed and startedconing, as a male, after about 8- production purposes. The plants were 9 years. Howeverothe smell and/or pollen placed in a site below the airport arrivals production caused such severe allergic hall in low light intensity, measuredlater at problems (asthma,headaches) to AV's 200 - 400 lux, resulting in rather etiolated mother that AV's father cut off the male foliage and a general deterioration in the conethat year (1993)and the following year plants'appearance.Within six months,i.e. (1994). (Apparently the island inhabitants at the end of 1997,eleven of the l2 plants arewell familiar with respiratoryproblems coned but three of them produced female arising during the cycad coning season.) cones. During 1998 these plants were The plant then failed to cone for several relocatedto a more appropriatearea with years until it suddenly produced a set of better lighting. These plants are being ovulate megasporophylls(1999), which monitored to see whether the "new" were successfullypollinated by AV. femaleschange back to their original male stafus, i.e. to ascertain whether or not a False cases ofsex changes cycad sex change is reversible or non- reversible. Since purely anecdotalreports may be elToneous,we have taken careto check all Four "new" sex change incidents reported incidents ofcycad sex changeas thoroughly as possible,where possible Cases I -3: Most readers of this inspecting the plants personally, getting magazinewill know of Loran Whitelock's confirmation from other parties, or California cycad garden.Whitelock Qters. examining photographic evidence. Some comm.) tells us that he has observedthree plants "bearing both male and female sex changes amongst the plants in his cones" on separatebranches have proved collection. One of two male Ceratozamia to be two plants growing very close to one matudaeplants, moved from a glasshouse another (see Figure 2 right). The to a gardensite in 1998,coned as a male in phenomenon of two embryos within one 1999but producedfemale cones in 2000 and cycad seedis not uncommon and, if these 2001. A known male specimen of both ultimately germinate, the possibility Encephalartos senticosus moved from of the plants fusing togetherat the seedling South Africa to Los Angeles produced only stage[chimaeras] is real. Suchfusedplants leavesfor 7 years,then coned regularly as would have a 50%ochance of being both a femalethereafter. Apot-bound male plant male and female. This appearsto be the of Zamia fairchildiana, salvaged from a situationin severalcases where claims have very dry glasshouseenvironment where it been made of "monoecious" cycads. f,! hadneverconedfor l0 - 15years, produced a male cone one year after being repotted TI

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