•WeusedArabidopsisthalianamutantsthatvaryinlignin,cellulose,orNcontentorinligninchemicalcomposition.
•Mutantshaveeitherlowlignincontent,lowcellulosecontent,ordifferentligninchemicalcomposition:alowratioofsyringyltoguaiacyl(S:G)units,ahighS:Gratio,5‐hydroxyguaiacylunits,orahighproportionofcinnamyl‐aldehydescomparedtowildtype.
•Wildtype(Columbia)Arabidopsisweregrownwithlow‐Nfertilizer(3mMKNO3‐N)orhigh‐Nfertilizer(15mMKNO3‐N)toproducestemtissuewitheitherhighorlowNcontent.
Useofanalyticalchemistrytoexaminecontrolsoverdecomposition
JennyM.Talbot1*,JamesNowick2,andKathleenTreseder11EcologyandEvolutionaryBiologyand2Chemistry,UniversityofCalifornia,*[email protected]
•DecompositionreleasesCO2totheatmosphereataratethatis10timesthecurrentrateduetoanthropogenicemissions.•Wemustunderstandthemechanismsoflitterdecompositioninordertoimprovepredictionsofcarbonsequestrationunderglobalchange.
•Plantchemistryshouldinfluenceratesoflitterdecompositionbycontrollingtheactivityofdecomposermicrobes.•Ligninisarecalcitrantaromaticcompoundthatsurroundsmorelabilecelluloseandproteininplantcellwalls.•Theamountandchemicalstructureofligninishypothesizedtoinfluencethedecayrateoflitterbycontrollingmicrobialaccesstolabilelittercomponents.
Objective: Todeterminethemechanismofinitiallitterchemistryeffectsondecompositionratebymappingthestructureandchemicalcompositionofplantcellwallsindecomposinglitter.
BACKGROUND
STUDYSYSTEM
1. LowcelluloselitterwilldecomposeslowerthanwildtypelitterduetolesslabileCsubstrateavailablefordecomposermicrobes.
2. Lowligninlitterwilldecomposefasterthanwildtypelitterduetolessprotectionofcelluloseandprotein.
3. LitterwilldecomposeintheorderlowS:G<wildtype<highS:G<5‐hydroxyguaiacylunits<cinnamyl‐aldehydelignincontentduetolesscondensedligninstructure.
4. LitterwithhighNcontentwilldecomposefasterthanlitterwithlowNcontentbyalleviatingtheNlimitationofdecomposermicrobes.
HYPOTHESES
•Quantitativeanalysisofchangesinthechemicalcompositionoflittermaterialduringdecomposition.•Developmentofaproceduretoquantifythedegradationofchemicalstructuresinlitterusingquantitative2DNMR.•Abilitytoidentifythemechanisticlinkbetweeninitiallitterchemistrytraitsanddecompositionrate.•Onechapterinadissertationandanassociatedpublicationinapeer‐reviewedjournal.
ANTICIPATEDPRODUCTWT
WT Lowcellulose Lowlignin
LowS:G
HighS:G
5‐hydroxy
CAH
LowN HighN
PlantType
%M
assloss
A
•Celluloseandnitrogencontentofplanttissueappeartocontrolratesofdecompositionintheborealzonebyactingasasubstratefordecomposers.•Ligninchemicalcompositionisastrongercontroloverlitterdecayratesthanlignincontentalone.•Intermsofligninchemistry,theamountofsyringylunitsandcinnamyl‐aldehydeunitsinligninarethebestpredictorsoflitterdecayrates.•Analysisofcellwallstructureindecomposedlitterisrequiredtodeterminethemechanismsdrivingthesepatterns.
DISCUSSION
Fig3.LitterbagsdecomposinginthefieldsiteinAlaskainJuly2008.
BA
Hypothesis1:Supported.ThelowcellulosemutantdecomposedslowerthanthewildtypeArabidopsis(P=0.008).
Hypothesis3:Partiallysupported.Therewasasignificanteffectofligninchemistryondecomposition(P=0.007).Stemsdecomposedintheorder:lowS:Gratio>wildtype>5‐hydroxyguaiacyl>highcinnamyl‐aldehydes>highS:Gratio.
Hypothesis4:Supported.PlantswithhighNcontentdecomposedfasterthanplantswithlowNcontent(P=0.002).
Fig4.MasslossofstemtissuedecomposedinanAlaskanborealforestfromJuly2008‐2009.Barsrepresentstandarderrors,n=1‐6.LettersrepresentTukeygroupings(P<0.05).
Hypothesis2:Notsupported.Thelowligninmutantdecomposedataratesimilartothewildtype.
•Over4000ArabidopsisplantsweregrownfromJanuary‐June2008.•Stemtissuefromeachplanttypewasharvestedandplacedin10cmx10cmlitterbagsmadeof1‐mmmesh.•Threetosixlitterbagsweremadeofeachplanttypeforatotalof30litterbags.•StemsweredecomposedfromJuly2008‐July2009intheborealforestofinteriorAlaska.•Decompositionrateofeachplanttypewascalculatedastotalmassloss.
METHODS
•Wewilltestthemechanismsunderlyinghypotheses1‐4byanalyzingthestructureandcompositionofwholecellwallsofdecomposedtissueforeachplanttype.•WholecellwallswillbedissolvedusingtheionicsolventisDMSO‐d6/1‐methylimidazole‐d6.•1‐methylimidazole‐d6willbesynthesizedbymethylatingimidazole‐d4withiodomethane‐d3.•Wewillquantifythecellwallstructureandthelossoflitterchemicalcomponentsduringdecompositionofeachplanttypeusing1Dand2DNMRspectroscopy.
FUTUREWORK
Fig1.ArabidopsisgrowingintheUCIgreenhouseApril‐July2008.
LowN
HighN
Fig2.WildtypeArabidopsisgrownunderhigh‐Norlow‐Nfertilizer.
050100150200250300350400450
050100150200250300350400450
Lignincon
tent
(mggDM
‐1)
Cellulosecon
tent
(mggDM
‐1)
Wildtype Lowcellulose
Lowlignin Wildtype Lowcellulose
Lowlignin
AA
B
AA
B
Planttype Planttype
5‐hydroxyguaiacyl
Guaiacyl(G) Syringyl(S) Cinnamyl‐aldehyde
O
OH
HO OCH3
OH
OH
HO OCH3
OH
OH
OCH3H3CO
OH
OH
OCH3
BAB
B BAB A A
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