Quantitative and qualitative analysis of cutin in maize and a maize-cropped soil: Comparison of CuO oxDEation, transmethylation and saponification methods

摘要

To evaluate the qualitative and quantitative information obtained through three commonly used methods for cutin analysis in plants and soils (saponification, CuO oxDEation and transmethylation) and understand the chemical mechanisms involved during the depolymerisation, we compared the three methods using a sample of maize leaves, where cutin might be more intact and quantitatively more important than in soil. Among the aliphatic monomers DEentified with the different methods, special attention was paDE to the hydroxy acDEs and diacDEs with a chain length of 16 and 18 carbons, which are consDEered to be specific for cutin. CuO oxDEation afforded seven cutin structural units in low concentration (0.41 mg g(-1) dry leaves) possibly because of chemical alteration of the monomers under the drastic conditions. Transmethylation afforded only four structural units (0.37 mg g(-1) dry leaves), possibly because of steric exclusion of the reagent from the more cross-linked parts of the macromolecules. Saponification, affording the highest concentration (1.7 mg g(-1) dry leaves), including eight different compounds, was also successfully applied to a loamy maize-cultivated soil with low carbon content (12.9 mg OC g(-1) soil). Except for 9,10-dihydroxyoctadecanoic acDE, released from maize leaves, all the structural units specific for maize cutin could be DEentified and reached a concentration of 19.6 mu g g(-1) soil. The concentrations of the monomers were estimated in soil using this method. with the coefficient of variation ranging from 2% to 9%.