Chemical composition of epicuticular wax crystals on the slippery zone in pitchers of five Nepenthes species and hybrids
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Plants of the carnivorous genus Nepenthes efficiently trap insects in leaf pitchers, mostly employing epicuticular wax crystals on the pitcher walls to make them slippery for the prey. In the present study, the compositions and micromorphologies of the wax crystals of five Nepenthes species and hybrids were analysed in order to test whether the chemical principles underlying this ecological function are widespread within the genus. Three wax layers could be distinguished within the Nepenthes pitcher cuticles: (1) the outermost part of the crystals forming the platelets visible in standard scanning electron microscopy, (2) the bottom portion of the epicuticular wax crystals, and (3) an intracuticular wax layer. The composition of the intracuticular wax differed significantly from that of the neighbouring epicuticular layer. The compositions of corresponding wax mixtures from all five Nepenthes species and hybrids were very similar, with almost equal amounts of very long chain aldehydes and primary alcohols. While triacontanal (C30 aldehyde) was prevailing in the epicuticular crystals of Nepenthes albomarginata and Nepenthes x intermedia, Nepenthes x superba and Nepenthes x henriana were found to have especially high percentages of dotriacontanal (C32 aldehyde). Nepenthes “khasiana” had an intermediate aldehyde composition with almost equal amounts of both chain lengths.
KeywordsAldehydes Chain length Cuticle Gas chromatography Intracuticular wax Mass spectrometry Scanning electron microscopy
polymerase chain reaction
Scanning electron microscopy
Technical assistance by the staff of the Botanical Garden of the University of Würzburg is gratefully acknowledged. The authors are indebted to Dr. Karin Glenz for providing sequence information for phylogenetic analysis. This work has been supported by the Sonderforschungsbereich 567 “Mechanismen der interspezifischen Interaktion von Organismen” (Germany) and the National Science and Engineering Research Council (Canada).
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