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Cutins of plant shoots and suberins, mostly present in roots could contribute to significant portions of stable soil organic matter. Their biomarker potential, residing in their unique compositions in different plant types, has been used previously to infer sources of organic matter in sediments. These aliphatic plant biopolyesters contain specific biomarkers, which may be used for tracing their fate in soils and sediments, when combined with stable 13 C isotope labelling. In order to evaluate the potential use of cutin and suberin biomarkers as indicators of shoot and root contributions from C 3 and C 4 plant origins, the objectives of this study were to 1) identify their constitutive monomers, which are specific for shoots and roots of maize (C 4 ) and wheat (C 3 ); 2) evaluate the 13 C differences between maize and wheat biomarkers. Mid-chain hydroxy carboxylic acids were mainly found in the aboveground biomass, while a,x-alkanedioic acids were only present in the roots. The differences in the isotopic composition of the specific monomers between wheat and maize plants (17-18% for shoot markers, 19% for root markers) were larger than those observed for bulk plant tissues and close to those observed for ligninderived phenols in other studies. These differences should make it possible to differentiate and quantify the different types and sources of organic matter in sediments and soils. In particular, the molecular and isotopic signatures of cutins and suberins can be used to evaluate the specific dynamics of root vs shoot tissues in soils using C 3 /C 4 chronosequences.

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