Sequential development of meristems in the embryo of Triticum durum. A DNA autoradiographic and cytophotometric analysis☆

[摘要] DNAlabelingwiththymidine-3HandDNAcytophotometryhavebeenusedtostudythesequentialdevelopmentofmeristemsintheembryoofTriticumdurum.Ithasbeenfoundthattheembryonicshootapexcompletesitsdevelopmentatca.63%watercontentintheseed;atseedmaturity,itconsistsexclusivelyofcellswith2C(G1)nuclearDNAcontent.Othermeristems—theapicesofprimaryrootandoftheseminalrootsofthefirstandsecondpair,primordiaofleaves1,2,and3—completetheirdevelopmentat47–48%seedwatercontent,orlower.Atseedmaturity,allleafprimordiaandmostapicesofthesecondpairrootsaremadeof2Ccellsonlywhereasthemeristemsoftheprimaryrootandofthefirstpairrootscontaindifferentproportionsof4C(G2)cellsinadditionto2Ccells.Ananalysisofthelabelingindexandofthemitoticindexinthemeristemsoftheembryoshasshownthat,atlatestagesofembryodevelopment,DNAsynthesisisstoppedearlierthanmitosis;buttheintervalbetweentheinhibitionofDNAsynthesisandtheinhibitionofmitosisisdifferentindifferentmeristems.Consequently,insomemeristems—leafprimordia,apicesofmostseminalrootsofthesecondpair—mitoticactivitylastslongenoughtodepletecompletelythemeristemof4C(G2)cells;intheremainingrootmeristems,this“depletionphase”islessefficient,thedegreeofitsefficiencydecreasingprogressivelyinthesuccession:rootsofsecondpair→rootsoffirstpair→primaryroot.Thesignificanceoftheseobservationsforstudiesondevelopmentalprocessesisdiscussed.

[学科分类] 生物科学（综合）