Chemical composition and ultrastructure of the foliar cuticular wax of two Brazilian cultivars of castor bean (Ricinus communis L.)

Abstract

The main goal of this study is to provide an overview of the composition and ultrastructure of the leaf cuticular wax from two Brazilian cultivars of castor bean (Ricinus communis L.), one of them drought tolerant. The cuticular wax constituents were identified by capillary gas chromatography-mass spectrometry (GC/MS), and the micromorphological characteristics of the wax were revealed by scanning electron microscopy (SEM). The cuticular wax content varied significantly between the cultivars (88.1–139.4μgcm−2). n-Alkanes were the main constituent class identified (ranging from 65.1 to 71.7% of total wax) with nonacosane as main compound. Triacontanoic acid and triacontanol were the major compounds found for n-fatty acid and n-primary alcohol classes, respectively. Lupeol, α-amyrin, β-amyrin and betulin triterpenes were found in both cultivars, but these compounds can be quantitatively differentiated from cultivars. SEM revealed that the cuticles of both cultivars are covered with a thick cuticular layer striated and are devoid of wax crystals on both surfaces.