Pesticide Effects on the Plant Cuticle: III. EPTC Effects on the Qualitative Composition of Brassica oleracea L. Leaf Cuticle1

Abstract

S-Ethyl dipropylthiocarbamate (EPTC, 2.24 kg/ha) altered wax composition on developing leaves of cabbage [ Brassica oleracea L. (Capitata group) cv. Market Prize], but did not affect cutin composition. The alkane, ketone and secondary alcohol content of the epicuticular wax was reduced and ester content increased. C 29 constituents (alkane, ketone, aldehyde and sec -alcohol) accounted for 72.5% (34.1 μ g/cm 2 ) and 40.2% (7.2 μ g/cm 2 ) of the epicuticular wax on control and EPTC-treated leaves respectively. Homlog composition within a chemical group was not changed. Chemical composition was similar for abaxial and adaxial leaf surfaces, and the EPTC-induced change in chemical composition was similar for both surfaces. In contrast with epicuticular wax, cuticular wax contained higher percentages of fatty acids and primary alcohols, and lower percentages of alkanes, and ketones. All constituents except the unidentified polar materials and fatty acids were lower in cuticular wax extracted from EPTC-treated than non-treated plants. The main component of the cutin fraction from both control and EPTC-treated plants was identified as dihydroxyhexadecanoic acid. Cutin acids were not quantitatively changed by the EPTC treatment.