Figure8-0CharlesDarwin- This portrait was made shortly after Darwinreturned to England from his voyage around the world.(TheGrangerCollection,NewYork)
Figure 8-0
4-day-oldDarwin:(1880)From experiments onLightoatseedlingcoleoptilephototropisrn,Darwinconciudedin188oColeoptitethata growth stimulusTsproducedinthecoleoptileSeedtip and is transmitted to thegrowthzone.IntactseedlingTip of coleoptileOpaguecap1cm(curvature)excisedontip(no curvature)(no curvature)RootsBovsen-Jensen(1g13)in1913,PBoysen.Jensendiscovered thatthe growthstimutuspasses throughgeiatinbutnotthroughWater-impermeable barrierssuchasmica.Mica sheetMica sheetTipremovedGelatinNormalinsertedinsertedbetweentipphototropicon darksideon lightsideand coleoptileCurvature(no curvature)(curvaturo)stumpremainspossiblePaal(1919)in1919,A.Paalprovidedevidence that the growthpromoting stimulusproducedinthetipwaschemicalinnature.TipremovedTip replacedGrowth curvatureon oneside ofdevelopswithoutcoleoptilestumpa unllateral lightstimulusWent (1926)in19z6.FW.Wentshowedthatthe activegrowth-promoting substance candiffuse intoagelatin blockHe aliso devised acoleoptile-bondinaassayforquantitativeauxinanalysisColeoptiletipsTips discarded:gelatinEach gelatinColeoptile bends inongelatincutupintosmallerblockplacedontotal darkness; angleblocksone side ofof curvature cancoleoptilestumpbe measured20(satajanean)(sabap) anein)2015151010n5O2468100.050.100.150.200.250.30NumberofcoleoptileIAAingelatinblock(mg/L)tips ongelatinFigure 8-1FIGURE 19,Tsearch
Figure 8-1
ciCH2-COOHCH,-COOHCH2-CH2-CH,-COOHNHHHIndole-3-aceticacid4-Chloroindole-3-aceticacidIndole-3-butyricacid(IAA)(4-CI-IAA)(IBA)FIGURE19.3Structure of three natural auxins.Indole-3-aceticacid (IAA)occurs inall plants,but other related compounds inplantshaveauxin activity.Peas,forexample,contain4-chloroindole-3-aceticacid.Mustardsand corn contain indole-3butyric acid (IBA)Figue 8-2
Figue 8-2
IAA1.lAAentersthecell eitherPlasmapassivelyintheundissociatedmembrane609089form(IAAH)orbysecondaryMLactivecotransportintheH+Permeaseanionicform(IAA-)HtHt-cotransportIAAYIAAHApex2H+CellwallK1IAAHPH5CytosolATPATP2.The cell wall ismaintained★H+个IAA3.Inthecytosol,whichhasaatanacidicpHbytheactivityneutral pH,theanionicformof theplasma membraneH+ATP(IAA)predominates.ATPase.PH7,★H+VacuoleATP★Ht★1IAA4.Theanions exitthe cell via000000000auxinanioneffluxcarriersthatareconcentratedattheL?4*basal endsofeachcell intheBaseIAAlongitudinalpathway2H+FIGURE19.13ThechemiosmoticmodelforIAAH4polar auxin transport.Shown hereis one cellin acolumn ofauxin-transporting cells.Figure 8-5(FromJacobsandGilbert1983.)AfP
Figure 8-5
(A)(B)(C)(D)Indole-3-pyruvicacidpathwayCOOHNH2HTryptophan(Trp)*TrpTrpdecarboxylasemonooxygenaseTrptransaminaseCOOHIANTAMOHNOHNH2HIndole-3-pyruvicacid (IPA)HIndole-3-acetaldoximeTryptamine(TAM)IPA1decarboxylaseBacterial pathwayAmineoxidaseNH2H工HIndole-3-acetaldehyde(iAld)Indole-3-acetamide (IAM)Indole-3-acetonitrile(lAN)IAlddehydrogenaseNitrilaseCOOH*IAMhydrolaseHIndole-3-aceticacid (IAA)FIGURE19.6Tryptophan-dependentpathwaysofIAAbiosynthesisinplantsandbacteria. The enzymes that are present only in bacteria are marked with an asterisk.Figure 8-6(AfterBartel1997.)
Figure 8-6