A quantitative study of mitotic figures in relation to development in the apical meristem of vegetative shoots of Coleus☆

[摘要] Aquantitative,round-the-clockstudywasmadeofvegetativeshootapexesofaclonalstockofColeusblumeiBenth.Aspecialaimofthestudywastofindmeaningful,exactrelationthatwouldbereproducibleyearafteryear.Suchrelationswehavefoundforthefollowing:1.1.Thereisadiurnalrhythmintheinitiationofleafprimordia,withaplastochronmorelikelytostartnearthemiddleofthedarkperiodthanatothertimessampled(Fig.4).2.2.Thenumberofmitoticfiguresintheapicalmeristem(heredefinedastheportionoftheshootdistaltotheyoungestleafprimordium)iscloselyandsignificantlycorrelatedwiththeheightoftheapicalmeristem,butthedistal10–20μofthemeristemconsistentlyhasfewermitoticfiguresthanmoreproximalregions(Fig.2).3.3.Theheightoftheapicalmeristemiscloselyandsignificantlycorrelatedwiththelengthoftheyoungestleafprimordium(Fig.1).4.4.Bycombiningtheabovefindingwiththepreviouslyreported(JacobsandMorrow,1957)correlationbetweenlengthsofunfoldedleavesandofyoungerprimordia,onecannowcollectapicalmeristemsofreasonablyspecificheightsbymeasuringtheolderleaveswithamillimeterruler.5.5.Contrarytoexpectationfromtheolderliterature,noevidencewasfoundforamarkeddiurnalrhythminthepercentageofcellsshowingmitoticfigures.Thelargeincreaseat11p.m.intheabsolutenumberofmitoticfigureswasareflection,rather,ofthemuchhigherapicalmeristematthattime(Fig.4).Acriticalexaminationrevealsthatsomeoftheapparentlydisparateresultsintheliteraturecouldhaveresultedfromanunrecognized,Coleus-like,diurnalrhythminthegrowthoftheapicalmeristem.

[学科分类] 生物科学（综合）