EEB alum, Dr. Jessica Budke (now director of the herbarium at the University of Tennessee) pursued her work on the cuticle in mosses, collaborating with colleagues at UBC to further our understanding of the chemistry of the cuticle. Following their paper in Phytochemistry, they also published a comparison with the cuticle of angiosperms. Vouchers are deposited in CONN herbarium.
Busta, L., J. M. Budke & R. Jetter. 2016. The moss Funaria hygrometrica has cuticular wax similar to vascular plants, with distinct composition on leafy gametophyte, calyptra and sporophyte capsule surfaces. Annals of botany 118: 511–522. pdf
Background and Aims. Aerial surfaces of land plants are covered with a waxy cuticle to protect against water loss. The amount and composition of cuticular waxes on moss surfaces had rarely been investigated. Accordingly, the degree of similarity between moss and vascular plant waxes, and between maternal and offspring moss structure waxes is unknown. To resolve these issues, this study aimed at providing a comprehensive analysis of the waxes on the leafy gametophyte, gametophyte calyptra and sporophyte capsule of the moss Funaria hygrometrica.
Methods. Waxes were extracted from the surfaces of leafy gametophytes, gametophyte calyptrae and sporophyte capsules, separated by gas chromatography, identified qualitatively with mass spectrometry, and quantified with flame ionization detection. Diagnostic mass spectral peaks were used to determine the isomer composition of wax esters.
Key Results. The surfaces of the leafy gametophyte, calyptra and sporophyte capsule of F. hygrometrica were covered with 094, 20 and 044 lg cm–2 wax, respectively. While each wax mixture was composed of mainly fatty acid alkyl esters, the waxes from maternal and offspring structures had unique compositional markers. b-Hydroxy fatty acid alkyl esters were limited to the leafy gametophyte and calyptra, while alkanes, aldehydes and diol esters were restricted to the sporophyte capsule. Ubiquitous fatty acids, alcohols, fatty acid alkyl esters, aldehydes and al- kanes were all found on at least one surface.
Conclusions. This is the first study to determine wax coverage (lg cm–2) on a moss surface, enabling direct com- parisons with vascular plants, which were shown to have an equal amount or more wax than F. hygrometrica. Wax ester biosynthesis is of particular importance in this species, and the ester-forming enzyme(s) in different parts of the moss may have different substrate preferences. Furthermore, the alkane-forming wax biosynthesis pathway, found widely in vascular plants, is active in the sporophyte capsule, but not in the leafy gametophyte or calyptra. Overall, wax composition and coverage on F. hygrometrica were similar to those reported for some vascular plant species, suggesting that the underlying biosynthetic processes in plants of both lineages were inherited from a com- mon ancestor.