Stratified analysis of cuticular waxes on fertile and sterile fronds of Gleichenella pectinata (Gleicheniaceae)

Gleichenella pectinata (Willd.) Ching is a fern species with monomorphic fronds (i.e., the sterile and fertile fronds are similar morphologically) and is widely distributed in South America. In the present study, the chemical composition of waxes on fertile and sterile fronds was analyzed and the epi and intracuticular wax portions were extracted separately. The total intracuticular wax content (55.85 ± 10.55 µg cm−2) was significantly higher than the total epicuticular content (44.36 ± 6.29 µg cm−2) of fronds. However, total wax content did not differ between sterile (92.54 ± 7.44 µg cm−2) and fertile (107.90 ± 17.26 µg cm−2) fronds. A total of 32 compounds belonging to seven different classes were identified: alkanes (C25-C27), esters (C34), aldehydes (C26-C32), ketones (C27-C31), free fatty acids (C14-C28), and primary (C18-C35) and secondary alcohols (C33-C35). The most abundant classes in the waxes were ketones, aldehydes, fatty acids, and primary alcohols, with nonacosan-10-one, octacosanal, and octacosanoic acid as the most prominent compounds. While no qualitative differences were observed, epicuticular and intracuticular waxes quantitatively accumulated more ketones (46.73 ± 16.17%) and aldehydes (27.83 ± 6.11%), respectively. The accumulation of these compounds in epicuticular waxes may be related to the formation of specific waxy crystalloids. In general, with regard to frond fertility, there was no difference in wax content or composition. Compared to other ferns lineages, the waxes found for G. pectinata showed very similarities with waxes from Osmunda regalis L., another basal leptosporangiate species. A great number of differences were found comparing the G. pectinata frond waxes with eusporangiate and recent leptosporangiate ferns.