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Experimental taxonomy in the Epacridaceae

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Jarman, SJ (1975) Experimental taxonomy in the Epacridaceae. PhD thesis, University of Tasmania.

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Abstract

One hundred and thirteen species or varieties were examined for the
presence of flavonoids in a chemotaxonomic study of the Epacridaceae.
Species were obtained from Tasmania, Victoria, New South Wales, New
Zealand and South America. Accessions from outside Tasmania contained
the same general complement of flavonoids as the Tasmanian species.
The characteristic flavonoids of the Epacridaceae are anthocyanins,
flavonols and leucoanthocyanidins but dihydroflavones and chalcones were
also present. Five common aglycones were identified i.e. cyanidin,
delphinidin, kaempferol, quercetin and myricetin but pelargonidin,
malvidin and possibly isorhamnetin were also present. The results
suggest that myricetin may be more widespread in nature than is normally
accepted, its apparent rarity being due to its lability under the
conditions used in its detection. Sugars involved in glycosylation
included galactose, glucose, arabinose, xylose, rhamnose and glucuronic
acid. Substitution occurred characteristically at position 3 but two
flavonols were glycosylated at position 5. Methylation was rare, and
3,5-diglycosylation in anthocyanins and 3,7-diglycosylation in flavonols
was not observed although 3-diglycosides were common. Four pigments
including cyanidin- and delphinidin-3-rhamnosylgalactoside, cyanidin-3-
xylosylarabinoside and quercetin-3-xylosylrhamnoside are reported for
the first time. Several species-specific compounds were observed and
particularly with flavonols, chromatographic patterns proved valuable
in species identification.
Glycosides were found to have greater importance taxonomically than
aglycones and the ratio of the major glycosidic types appears to have
phylogenetic as well as taxonomic significance. The results suggest
that anthocyanin and flavonol galactosides are more advanced in the
family than anthocyanin arabinosides and flavonol glucnronides
respectively. A correlation between chemical and cytological data
enabled an evolutionary index to be calculated for 36 species, and a
chemical comparison between the two subfamilies supports the opinion
that the Styphelieae is more advanced than the Epacrideae.
Three genera, Epacris, Cyathodes and Monotoca, have been examined
in more detail than the remaining genera, and the contribution of
flavonoid compounds to their taxonomy is discussed. Two new species
are described for the first time.
Several numerical analyses were carried out on the chemical data
and a discussion of the results is given.
A comparison between the Epacridaceae and published data for the
related family, the Ericaceae, reveals some pronounced chemical
differences, although the two are linked by the common occurrence of
anthocyanin and flavonol galactosides and arabinosides. Evidence
suggests that evolution towards more complex aglycones has occurred in
the Ericaceae whereas greater variation in glycosylation is apparent
in the Epacridaceae.

Item Type: Thesis (PhD)
Keywords: Epacridaceae
Copyright Holders: The Author
Copyright Information:

Copyright 1975 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.) - University of Tasmania, 1975. Including bibliography

Date Deposited: 19 Dec 2014 02:23
Last Modified: 28 Jun 2017 01:51
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