國產(chǎn)香茶菜屬植物染色體數(shù)的初步研究

國產(chǎn)香茶菜屬植物染色體數(shù)的初步研究

獨立（schrod.exer，2008；leandmille，1994），第（shanghai，1840；kud8，1929；codd，1968，1984，1986），基本貨物運動的證據(jù)：一類和二類（證據(jù)和粗糙的、粗糙的和低王國），第（證據(jù)和自由的）。（li，1988；liandheld，1994；haley等人，2004），第100個二級貨物運動可分為以下幾個部分：第8個或第8個，第8個或第8個。馬修，2008），反映葉明的80個案例（ca，1988；liandheld，1994）。它是中國的第八個省級人口最多的地方（zhongetal.2010；xiangandli，2012；chenetal.2014）。Thevalueofcytologicaldatainthestudyofplantevolution,diversificationandphylogenyhaslongbeenrecognized,andchromosomecytologyisconsideredasimportantevidenceinresolvingrelationshipsamongthemintfamily(Bushnell,1936;Elena-Roselló,1981;Gill,1983;Cantino,1985;Funamoto,2007;Funamotoetal.,2008,2009;FunamotoandSmirnov,2011).DespitethepotentialsystematicimportanceofchromosomaldataforIsodon,thegenusiscytologicallypoorlystudied(Table1).ThefirstpublishedaccountofchromosomaldatainIsodoncanbetracedbackto1950whenSuzuka(1950)reportedthechromosomenumberofPlectranthusjaponicus(Burm.f.)Koidz[=I.japonicus(Burm.f.)H.Hara]tobe2n=24.Wakabayashi(1973)identified2n=24forRabdosiaumbrosa(Maxim.)H.Haravar.hakusanensis(Kud8)H.Hara[=I.umbrosus(Maxim.)H.Haravar.hakusanensis(Kud8)K.Asano],andSokolovskayaetal.(1986)reported2n=24forbothI.japonicusandI.excisus(Maxim.)Kud8.InhiscytologicalstudyofthefloraofCameroonsMountain,Morton(1993)reported2n=42(x=7)forI.ramosissimus(Hook.f.)Codd,indicatingittobehexaploid.Later,chromosomenumbersofsevenspeciesandsixvarietiesofIsodonoccurringinJapanwerestudiedbyYamashiroetal.(2005)andallofthetaxahad2n=24chromosomes.AlthoughmostofthetaxaofIsodonaredistributedinChina,onlyfourspeciesandtwovarietieshavehadtheirchromosomenumbersreportedsofar(Table1).JinandSha(2004)andZhaoetal.(2007)identified2n=24forI.japonicusvar.glaucocalyx(Maxim.)H.W.LiandI.rubescens(Hemsl.)H.Hara,respectively.Mostrecently,Huang(2011)checkedthechromosomesoftwospeciesandtwovarietiesofthegenusandreported2n=24forI.serra(Maxim.)Kud8,I.lophanthoides(Buch.-Ham.exD.Don)H.Haravar.gerardianus(Benth.)H.Hara,andI.lophanthoidesvar.graciliflorus(Benth.)H.Hara,but2n=36forI.lophanthoidesvar.lophanthoides,whichsuggestedthisspeciestobetriploid.IdenticalchromosomenumbersforI.lophanthoidesvar.gerardianusandI.lophanthoidesvar.gracilifloruswerefurtherverifiedbyZhangetal.(2012).Theremainingtaxaofthegenus,especiallythosedistributedinSouthwesternChina,havenotyetbeeninvestigatedcytologically.Thus,furtherstudiestoobtainbasicinformationarebadlyneeded.ThemainobjectiveofpresentcontributionistoexaminethechromosomenumbersofseveralrepresentativesofIsodonfromChina,especiallyfromtheregionofHengduanMountains.Wealsohopetoevaluatethesystematicsignificanceofchromosomedataforthegenus.ItformsapartofourresearchonthetaxonomyofIsodon(XiangandLiu,2012),andthecytologicalstudyofLamiaceaefromEasternAsia(FunamotoandOgawa,2004;Funamoto,2007;Funamotoetal.,2008,2009;FunamotoandSmirnov,2011).1細結構面向cowellingMericarpsof16populationsbelongingto13taxa(11speciesandtwovarieties)ofIsodonwerecollectedfromplantsgrowingundernaturalconditionsinGansu,Sichuan,Tibet,andYunnan,China.VoucherspecimenswerekeptatHerbariumofKunmingInstituteofBotany,ChineseAcademyofSciences(KUN).NomenclatureofIsodoninthisstudyfollowsLi&Hedge(1994),exceptforI.polystachys(Y.Z.Sun)H.HarawhichishereretainedasadistinctspecieswhereasLi(1988)andLi&Hedge(1994)reduceditasasynonymofI.coetsa(Buch.-Ham.exD.Don)Kud8.Additionally,taxonomictreatmentofI.lophanthoidesvar.gerardianusfollowstherevisionofSuddeeetal.(2004),inwhichthevarietywastreatedasasynonymofI.lophanthoidesvar.graciliflorus.Themericarpsweresownonwetfilterpaperinpetri-dishesforgermination.Freshlygrowingroottipswerecollectedfromtheabovematerialsforcytologicalinvestigations.Theywerecutoff5-10mmlongandpretreatedin2mmol·L-18-hydroxyquinolinefor4hat20℃,andthenfixedin45%aceticacidfor10minatabout2℃.Finallytheyweremaceratedinamixtureof45%aceticacidand1mol·L-1hydrochloricacid(1∶1)for20-23satabout60℃,andstainedin2%aceto-orceinforover30minatroomtemperatureinamoistchamberwith45%aceticacid.Slidepreparationsweremadeusingtheconventionalaceto-orceinsquashmethodsandwerefaintlyheatedunderanalcoholframefor1-2sbeforeobservation(FunamotoandOgawa,2004).PhotomicrographsweretakenfromfreshlypreparedslideglassesusingOLYMPUSDigitalCamera(DP72-SET-A-2)System.Forthedeterminationofchromosomenumbers,atleastfiveindividualsofeachpopulationwereinvestigated,andforeachindividual,chromosomenumbersof5-10cellswerecountedatsomaticmetaphase.Chromosomesattherestingstateandmitoticprophasewereobservedaswell.DescriptionofmorphologicalcharacteristicsoftherestingnucleifollowedtheclassificationofTanaka(1971).2erwelling,which-關于“兩關系”Chromosomenumbersofthe13taxaarelistedinTable2andmorphologyandsizeofthechromosomesareillustratedinFigs.1-2.Allspeciesandvarietieshavethechromosomenumber2n=24,exceptforI.coetsa(2n=24,48).Thus,x=12canbeinferredasthebasicchromosomenumberofIsodonfromChina.TheresultlargelycorroboratesthatofYamashiroetal.(2005)whocontributedtothechromosomenumbersofIsodonoccurringinJapan.Intheirstudy,allsevenspeciesandsixvarietiesfromJapanhave2n=24chromosomes.ConsideringthatchromosomesofIsodonareofunclearcentromeresandrathersmallsizes(generallysmallerthan2μm,seeFigs.1-2),whichisinagreementwithpreviousstudies(JinandSha,2004;Yamashiroetal.,2005;Huang,2011;Zhangetal.,2012),detailedkaryotypeanalysiswasnotimplementedsuccessfullyinpresentstudy.AccordingtotheclassificationofTanaka(1971),therestingnucleioftheIsodonspeciesstudiedbelongtotherodprochromosometype.Rod-shapedheteropycnoticbodieswithvariedsizeandshapecanbeobserved.Thesurfacesoftheprochromosomesaresmooth.Aheterochromaticsegmentlocatedintheproximalregionofthechromosomeformingbyeachprochromosomecanbeobservedaswell.ForalltaxaexceptI.lophanthoidesvar.graciliflorus,chromosomenumbershavenotbeencountedbefore,andourresult(Table2;Fig.1H,I)isconsistentwithpreviousfindingsthatI.lophanthoidesvar.graciliflorushas2n=24chromosomes(Huang,2011;Zhangetal.,2012).Noticeably,thenumber2n=36wasreportedbyHuang(2011)fromI.lophanthodiesvar.lophanthoides,suggestingthistaxatobetriploid.TheresultcanbeconfirmedbyevidencefromthepreviouspalynologicalsurveyofI.lophanthodiesthatmostofitspollengrainswerefoundtobeabortivetetradswithvariousshapes(Chenetal.,2000;Huang,2011),andfromourobservationinthewildthatmostofthemericarpsofthespecieswerealsoabortive.Ononehand,triploidyisalwaysthoughttobeahindrancetotheoriginoffertilespeciesduetothehighorderofmeioticirregularitywhichitbringsabout(Storey,1950).Ontheotherhand,I.lophanthodies,distributedinwethills,forestsandravinesinSouthernChina,isoneofthemostwidespreadspeciesofIsodon.ItcanalsobefoundinIndia,Myanmar,Nepal,Thailand,andVietnam(LiandHedge,1994).Thus,itisworthytofurtherelucidatethereproductionmechanismofI.lophanthodiesbasedonamultidisciplinaryinvestigation.ThemonotypicgenusSkapanthusC.Y.Wu&H.W.LiwasdelimitedbyLi(1975)andWuandLi(1977)toaccommodatethespeciespreviouslyknownasPlectranthusoreophilusDiels,asitwasreadilydifferentiatedfromPlectranthusbyseveralmorphologicalcharacters.Later,thegenuswastreatedasasynonymofIsodonbyPatonandRyding(1998).Here,wecountedthechromosomenumberofI.oreophilus(Diels)A.J.Paton&Rydingvar.elongatus(Hand.-Mazz.)A.J.Paton&RydingandtheresultprovidesadditionalevidenceforitsaccommodationinIsodon.LikemostIsodonspecies,I.oreophilusvar.elongatushas2n=24chromosomes(Table2;Fig.2A,B).Inaddition,thetreatmentisalsosupportedbyrecentmolecularphylogeneticstudythatspeciesofIsodonandSkapanthusformedagroupwithstrongsupportvaluesinallanalyses(Zhongetal.,2010).ChromosomesnumbersofthreepopulationsofI.coetsafromYunnanprovincewereinvestigated.Thechromosomenumberof2n=24fromShangri-La(Table2;Fig.1B)andSongming(Table2;Fig.1C)ishalfofthatofthecytotype2n=48fromLongling(Table2;Fig.1D).Thechromosomenumber2n=48inthegenusisalsoreportedhereforthefirsttime.Withtheassumedbasicnumberofx=12forIsodon,bothdiploidyandtetraploidyexistwithinindividualsofI.coetsa.Theformationof