Plant polyphenols - Implications of different sampling, storage and sample processing in BEF experiments.
Created at: 2012-02-13
Initial title: The impact of storage conditions on leaf contents of tannin and total phenolics and their relationships with other functional traits
Envisaged journal: Plant polyphenols – implications of different sampling, storage and sample processing in biodiversity-ecosystem functioning experiments D. Eichenberg, C. Ristok, W. Kröber, H. Bruelheide; Chemistry and Ecology (accepted March 2014); doi: 10.1080/02757540.2014.894987 url: http://dx.doi.org/10.1080/02757540.2014.894987
Envisaged date: 2014-02-13
We analyzed tannin and non-tannin phenolics contents of 20 subtropical tree species from East China with the aims to assess the impact of two different sample storage and processing methods and to relate them to other plant functional traits. We collected a set of leaf samples of 20 species from 10 different families in 2009 and stored them under dry conditions. The sampling was repeated in 2011 using an optimized sample processing protocol involving lyophylisation. Total phenolics and tannin content were quantified by the Prussian Blue assay and the radial diffusion method for increased sensitivity, respectively and compared among the two different methods of sample processing. We found that the impact of different sample storage and processing conditions on the content of total phenolics and tannin was less pronounced than expected from the suboptimal sample treatment. Variance components analysis revealed that a considerable amount of variance in the contents of secondary compounds was explained by the taxonomic levels of ‘family’ as well as ‘genus’. We showed that, in these secondary metabolites, the taxonomic conservation was more pronounced than in other traits from the leaf economics spectrum known for the investigated species. After accounting for phylogenetic relatedness, both sets showed no significant difference in the mean total phenolics content but differed significantly in tannin content. In conclusion, for ecological studies including species from a wide variety of families and genera, the adverse effects of suboptimal sample treatment were largely overridden by the variation brought about by phylogeny. Nevertheless, total phenolics content turned out to be much more robust than tannin content. In a non-metric multi dimensional scaling (NMDS) analysis we found total phenolics and tannin content to be strongly collinear, but negatively correlated with leaf toughness, indicating a trade-off in investment for defense between chemical and mechanical strategies. In our data set, deciduous species possessed significantly higher amounts of total phenolics and tannin than evergreen species, although evergreen leaves displayed higher leaf toughness. Additionally, we encountered positive relationships to the contents of leaf macro-nutrients and specific leaf area (SLA). Because total phenolics and tannin content were strongly correlated we advocate a focus on total phenolics content rather than tannin content in, for example, trans-experimental studies.
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