Primary plant surfaces are coated with hydrophobic cuticular waxes to minimize non-stomatal water loss. Wax compositions differ greatly between plant species and, in the few species studied systematically so far, also between organs, tissues, and developmental stages. However, the wax mixtures of more species in diverse plant families must be investigated to assess overall wax variability, and ultimately to correlate organ-specific composition with local water barrier properties. Here, we present comprehensive analyses of the waxes covering five organs of Taraxacum officinale (dandelion), to help close a gap in our understanding of wax chemistry in the Asteraceae family. First, novel wax constituents of the petal wax were identified as C25 6,8- and 8,10-ketols as well as C27 6,8- and 8,10-ketols. Nine other component classes (fatty acids, primary alcohols, esters, aldehydes, alkanes, triterpenols, triterpene acetates, sterols, and tocopherols) were detected in the wax mixtures covering leaves, peduncles, and petals, as well as fruit beaks and pappi. Wax coverages varied from 5 μg/cm2 on peduncles to 37 μg/cm2 on petals. Alcohols predominated in leaf wax, while both alcohols and alkanes were found in similar amounts on peduncles and petals, and mainly alkanes on the fruit beaks and pappi. Chain length distributions within the wax compound classes were similar between organs, centered around C26 for fatty acids, alcohols, and aldehydes, and C29 for alkanes. However, the quantities of homologs with longer chain lengths varied substantially between organs, reaching well beyond C30 on all surfaces except leaves, suggesting differences in elongation enzymes determining the alkyl chain structures. The detailed wax profiles presented here will serve as basis for future investigations into wax biosynthesis in the Asteraceae and into wax functions on different dandelion organs.
Bibliographical noteFunding Information:
This work was supported by the National Natural Science Foundation of China (grant number 31670407, 2016) and the Natural Science and Engineering Research Council of Canada (Discovery grant #262461). Yanjun Guo conducted this study as a visiting scholar with financial support from Chongqing Municipal Education Commission Fund.
© 2017 Elsevier Masson SAS
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- Cuticular wax
- Structure elucidation
- Taraxacum officinale (dandelion)