The morphology and chemical composition of cuticular waxes in some Brazilian liverworts and mosses

The cuticle, by ensuring protection against water loss, was a key innovation in plant terrestrialisation. This layer is characterised by the cutin matrix embedded and covered with cuticular waxes. In this study we describe the cuticular waxes on gametophytes of several species of liverworts and mosses, including Brazilian endemics. Cuticular waxes from 34 species from different locations in the São Paulo state, Brazil, were analysed by gas chromatography coupled with mass spectrometry. The compounds were identified based on mass spectra fragmentation. The morphology of the epicuticular waxes was analysed using scanning electron microscopy. The wax content in the liverwort species varied from 0.1 to 4 μg cm⁻², while in mosses the values ranged from 0.02 to 0.6 μg cm⁻². The main classes of wax compounds were fatty acids, alkanes, and primary alcohols. Aldehydes, alkenes, esters, ketones, triterpenes, a diacid and a secondary alcohol had a more restricted distribution. The morphology of the epicuticular waxes was predominately of the film type. In general, wax content was higher in the liverworts than in the mosses. Fatty acids and alkanes were the most common class whilst alkenes, ketones, diacid, and a secondary alcohol are described for the first time as wax compounds in bryophyte gametophytes.