Introduction Plumbagin and 7-methyljuglone are characteristic acetogenic (= derived from acetic acid) naphthoquinones (see Scheme 1) that allow a chemotaxonomic delimitation and the distinction between sundew (Drosera L.) species or species groups (Zenk et al. 1969; Durand & Zenk 1974; Culham & Gornall 1994; Schlauer et al. 2005). This has recently (Schlauer et al. 2017) been applied to several Australian species in Drosera sections Arachnopus Planch. (the “D. indica L. complex”) and Coelophylla Planch. (D. glanduligera Lehm.). By extending these studies to further accessions and species, some new and interesting insights into the chemical diversity of the genus were gained. In addition, the characteristic leaf and stem emergences of all examined Arachnopus species arefeatured in detail by microscopy images.

Excerpt: Drosera indica emergences Figure 7: Drosera indica. Background: mature stem with leaf bases showing lateral “stipules” (actually emergences) at leaf bases (red arrows and oval); A: double-tipped cap with elongated stalk at leaf base with stalked glands and short double-tipped caps; B: mushroom-emergence (left), shorter stalked glands and medium sized double-tipped cap. We produced two documentary films for YouTube, to accompany the article regarding the emergences. Just click on the pictures to view the films on YouTube: &

References Culham, A., and Gornall, R.J. 1994. The taxonomic significance of naphthoquinones in the Droseraceae. Biochem. Syst. Ecol. 22: 507-515. Durand, R., and Zenk, M.H. 1974. The homogentisate ring-cleavage pathway in the biosynthesis of acetate-derived naphthoquinones of the Droseraceae. Phytochemistry 13: 1483-1492. Putalun, W., Udomsin, O., Yusakul, G., Juengwatanatrakul, T., Sakamoto, S., and Tanaka, H. 2010. Enhanced plumbagin production from in vitro cultures of Drosera burmanii using elicitation. Biotechnol. Lett. 32: 721-724. Schlauer, J., and Fleischmann, A. 2016. Chemical evidence for hybridity in Drosera (Droseraceae). Biochem. Syst. Ecol. 66: 33-36. Schlauer, J., Hartmeyer, S.R.H., and Hartmeyer, I. 2017. Unexpected discovery of 7-methyljuglone (ramentaceone) in several Australian sundews. Carniv. Pl. Newslett. 46: 20-22. Schlauer, J., Nerz, J., and Rischer, H. 2005. Carnivorous plant chemistry. Acta Botanica Gallica 152: 187-195. Zenk, M.H., Fübringer, M., and Steglich, W. 1969. Occurrence and distribution of 7-methyljuglone and plumbagin in the Droseraceae. Phytochemistry 8: 2199-2200.