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MorphologyofTheRicePlant（胚根鞘）,acoveringenclosingtheradicle（胚根）orprimaryroot,protrudesfirst.Fig.1-Thecoleorhizaprotrudesfirst.Shortlyafterthecoleorhizaappears,theradicleorprimaryrootbreaksthroughthecovering.Fig.2-Radicleorprimaryrootbreaksthroughthecovering.Twoormoresparselybranchedseminalroots（种子根）follow.Theserootseventuallydieandarereplacedbymanysecondaryadventitiousroots（次生不定根）.Fig.3-SeminalrootsIftheseedgerminatesinwater,thecoleoptile,acoveringenclosingtheyoungshoot,emergesaheadofthecoleorhiza.Thecoleoptile（胚芽鞘）emergesasataperedcylinder（圆钻型）.Fig.4-Coleoptileemergingasataperedcylinder.SeedlingThemesocotyl（中胚轴）orbasalportionofthecoleoptileelongateswhentheseedgerminatesinsoil,andindarkness.Itpushesthecoleoptileabovethesoilsurface.Fig.5-Mesocotylpushingthecoleoptileabovethesoilsurface.Thefirstseedlingleaf,orprimaryleaf,emergesfromthegrowingseed.Itisgreenandshapedlikeacylinder.Ithasnoblade.Thesecondleafisacompleteleaf.Itisdifferentiatedintoaleafbladeandaleafsheath.Fig.6-Firstandsecondseedlingleaf.TillerTheseedlingwillgrowanddevelopbranchedtillers.Partsofthericetillerincludetheroots,culmandleaves.Maturerootsofthericeplantarefibrousandproducesmallerrootscalledrootlets.Allrootshaveroothairstoabsorbmoistureandnutrients.Fig.7-Partsofthericetiller.Therearetwokindsofmatureroots:1.secondaryadventitiousroots;2.adventitiousproproots（地上不定根）.Fig.8-Typesofroots.Secondaryadventitiousrootsareproducedfromtheundergroundnodesofyoungtillers.Fig.9-Secondaryadventitiousroots.Astheplantgrows,coarseadventitiousproprootsoftenformabovethesoilsurfaceinwhorls（轮生方式)fromthenodesoftheculm.Fig.10-Adventitiousproproots.CulmTheculm,orjointedstemoftherice,ismadeupofaseriesofnodesandinternodes.Fig.11-Culm,nodes,andinternodes.Younginternodesaresmoothandsolid.Matureinternodesarehollowandfinelygrooved(槽沟的）withasmoothoutersurface.Generally,internodesincreaseinlengthfromthelowertotheupperportionsoftheplant.Thelowerinternodesattheplantbaseareshortandthick.Fig.12-Youngandmatureinternodes.Thenodeisthesolidportionoftheculm.Thenodeornodalregionbearsaleafandabud.Thebudisattachedtotheupperportionofthenodeandisenclosedbytheleafsheath.Thebudmaygiverisetoaleaforatiller.Fig.13-Leaf,node,andbud.Earlytillersarisefromthemainculminanalternatepattern.Primarytillersoriginatefromthelowermostnodesandgiverisetosecondarytillers.Secondarytillersproducetertiarytillers.Fig.14-Primarytillers.Fig.15-Secondarytillers.Fig.16-Tertiarytillers.LeafThenodeornodalregionoftheculmwillbearaleaf.Fig.17-Leaf.Leavesarebornealternatelyontheculminoppositedirections.Oneleafisproducedateachnode.Varietiesdifferinthenumberofleavesproduced.Fig.18-Leavesalternateontheculminoppositedirections.Thetopmostleafbelowthepanicleistheflagleaf.Theflagleafcontributeslargelytothefillingofgrainsbecauseitsuppliesphotosyntheticproducts,mainlytothepanicle.Fig.19-Flagleaf.Theleafsheathandleafbladearecontinuous.Fig.20-Leafsheathandblade.Acircularcollarjoinstheleafbladeandtheleafsheath.Fig.21-Leafcollar（叶颈）.Mostleavespossesssmall,pairedear-likeappendagesoneithersideofthebaseoftheblade.Theseappendagesarecalledauricles.Auriclesmaynotbepresentonolderleaves.Anotherleafappendageistheligule,apaperymembraneattheinsidejuncturebetweentheleafsheathandtheblade.Itcanhaveeitherasmoothorhair-likesurface.Thelength,color,andshapeoftheliguledifferaccordingtovariety.Fig.27-Liguleandauricle.Althoughsimilar,riceseedlingsaredifferentfromcommongrasses.Whilericeplantshavebothauriclesandligules,commongrassyweedsfoundinricefieldsnormallydonothavethesefeatures.Thesecharacteristicsareoftenhelpfulinidentifyingweedsinricefieldswhentheplantsareyoung.Fig.28-Riceandgrassyweedcomparison.Theleafsheathiswrappedaroundtheculmabovethenode.Fig.22-Leafsheathandculm.Theswellingatthebaseoftheleafsheath,justabovethenode,isthesheathpulvinus（叶鞘座）.Itissometimesincorrectlyreferredtoasthenode.Fig.23-Sheathpulvinus.Leafbladesaregenerallyflat.Varietiesdifferinbladelength,width,thickness,area,shape,color,angleandpubescence.Fig.24-DifferentvarietieswithvaryingbladecharacteristicsWithmanyparallelveinsontheuppersurfaceoftheleaf,theundersideoftheleafbladeissmoothwithaprominentridgeinthemiddle;themidrib.Fig.25-Parallelveins(叶脉）onuppersurface.Fig.26-Leafmidrib（叶筋）.PanicleandSpikeletsTheterminalcomponentofthericetillerisaninflorescencecallthepanicle.Theinflorescenceorpanicleisborneontheuppermostinternodeoftheculm.Thepaniclebearsricespikelets（小穗）,whichdevelopintograins.Thepaniclebaseoftenappearsasahairlikeringandisusedasadividingpointinmeasuringculmandpaniclelength.Thepaniclebaseisoftencalledtheneck（穗颈）.Thepanicleaxisiscontinuousandhollowexceptatthenodeswherebranchesareborne.Theswellingsatthepanicleaxiswherethebranchesarebornearereferredtoasthepaniclepulvinus.Eachnodeonthemainpanicleaxisgivesrisetoprimarybrancheswhichinturnbearssecondarybranches.Primarybranchesmaybearrangedsinglyorinpairs.Thepaniclesbearspikelets,mostofwhichdevelopintograin