Characterization and biosynthesis of non-degradable polymers in plant cuticles

The structure and monomeric composition of the highly aliphatic and non-sap onifiable fraction of cutans isolated from the leaf cuticles of Agave ameri cana L. and Clivia miniata Reg. have been elucidated. Spectroscopic Fourier transform infrared and C-13-nuclear magnetic resonance, calorimetric and X -ray diffraction studies, together with biopolymer analysis after exhaustiv e ozonolysis, showed that the cutan fraction consists of an amorphous three -dimensional network linked by ether bonds containing double bonds and free carboxylic acid functions. Data obtained from fatty acid sorption indicate d that the new biopolymer investigated here has a highly hydrophobic charac ter constituting an additional barrier biopolymer in those cuticles where i t is present. Labelled [C-14]linoleic acid was preferentially incorporated into the non-ester part of C. miniata leaf disks in comparison with the cut in fraction of the cuticular membrane. This indicates that the cis-pentadie ne system of polyunsaturated fatty acids is involved in the formation of in tramolecular linkages, mainly ether bonds, of the aliphatic biopolymer.