AOBPreview originally published online on March 6, 2006
Annals of Botany 2006 97(6):1017-1044; doi:10.1093/aob/mcl048
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Frequency of Cyanogenesis in Tropical Rainforests of Far North Queensland, Australia
School of Botany, The University of Melbourne, Victoria, 3010, Australia
* For correspondence. E-mail rem{at}unimelb.edu.au
Received: 14 January 2005 Returned for revision: 21 December 2005 Accepted: 23 January 2006 Published electronically: 6 March 2006
• Background and Aims Plant cyanogenesis is the release of toxic cyanide from endogenous cyanide-containing compounds, typically cyanogenic glycosides. Despite a large body of phytochemical, taxonomic and ecological work on cyanogenic species, little is known of their frequency in natural plant communities. This study aimed to investigate the frequency of cyanogenesis in Australian tropical rainforests. Secondary aims were to quantify the cyanogenic glycoside content of tissues, to investigate intra-plant and intra-population variation in cyanogenic glycoside concentration and to appraise the potential chemotaxonomic significance of any findings in relation to the distribution of cyanogenesis in related taxa.
• Methods All species in six 200 m2 plots at each of five sites across lowland, upland and highland tropical rainforest were screened for cyanogenesis using Feigl–Anger indicator papers. The concentrations of cyanogenic glycosides were accurately determined for all cyanogenic individuals.
• Key Results Over 400 species from 87 plant families were screened. Overall, 18 species (4·5 %) were cyanogenic, accounting for 7·3 % of total stem basal area. Cyanogenesis has not previously been reported for 17 of the 18 species, 13 of which are endemic to Australia. Several species belong to plant families or orders in which cyanogenesis has been little reported, if at all (e.g. Elaeocarpaceae, Myrsinaceae, Araliaceae and Lamiaceae). A number of species contained concentrations of cyanogenic glycosides among the highest ever reported for mature leaves—up to 5·2 mg CN g–1 d. wt, for example, in leaves of Elaeocarpus sericopetalus. There was significant variation in cyanogenic glycoside concentration within individuals; young leaves and reproductive tissues typically had higher cyanogen content. In addition, there was substantial variation in cyanogenic glycoside content within populations of single species.
• Conclusions This study expands the limited knowledge of the frequency of cyanogenesis in natural plant communities, includes novel reports of cyanogenesis among a range of taxa and characterizes patterns in intra-plant and intra-population variation of cyanogensis.
Key words: Australia, ß-glycosidase, chemotaxonomy, cyanogenic glycoside, cyanogenesis, defence, hydrogen cyanide, polymorphism, Queensland, screening, secondary metabolite, tropical rainforest
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