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Wound responses of Eucalyptus globulus and E. nitens : anatomy and chemistry

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Eyles, Alieta (2003) Wound responses of Eucalyptus globulus and E. nitens : anatomy and chemistry. PhD thesis, University of Tasmania.

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Abstract

The anatomical and chemical host responses of two economically important Eucalyptus
species grown in southern Australia (E globulus and E. nitens) to different wounding
treatments (mechanical, chemical and biological) were investigated. Initially, the project
primarily focused on the role of kino veins as barrier zones in eucalypt tree defence but then
later also included the characterization of the new tissue formed subsequent to wounding, an
area of study previously never been studied in any eucalypt species.
The developmental anatomy and structure of kino veins was examined in three juvenile
Eucalyptus species (E. nitens, E. globulus and E. obliqua) to treatment with an ethylenereleasing
compound, 2-chloroethyl phosphonic acid (CEPA). Unlike E. globulus and
E. obliqua, E. nitens failed to produce kino veins in response to the hormone treatment,
confirming anecdotal evidence that this species does not readily form kino veins. During this
study, histochemical stains including p-dimethylaminocinnamaldehyde (DMACA) and
Coomassie brilliant blue G-250 (BBG-250) were refined to allow the localization of
condensed tannins and hydolyzable tannins, respectively in wood sections. The production of dark extractives (non-structural components of wood and bark) was
regularly observed as part of the wound response in both the phloem and/or xylem tissue and
regardless of the cause of injury. The various wound treatments examined included drill
wounding with fungal inoculations, dry ice wounding, natural infection to stem canker
(Cytonaema sp.) and prune wounding. Analysis of dark extractives extracted from the new
tissue formed after wounding using gas chromatography combined with mass spectrometry
(GC-MS), high performance liquid chromatography (HPLC-UV) coupled to negative ion
electrospray mass spectrometry (ESI-MS) revealed that a complex range of secondary
metabolites was present, including hydrolyzable tannins, proanthocyanidins, flavonone
glycoside, stilbene glycosides, formylated phloroglucinol compounds (FPCs) and volatile
terpenes. These compounds were either undetectable in healthy tissue or else present at significantly lower concentrations than in wound-associated tissue. In particular, the
detection of FPCs in the wound-associated wood was a novel finding, hitherto detected in the
leaves of various eucalypt species. We suggest that the diverse range of secondary
metabolites detected in the wound-associated tissue may have a multi-functional role in
relation to tree wound repair and defence. Crude wound wood extracts were shown to
possess in vitro antimicrobial activity against decay fungi and gram-positive bacteria as well
as in vitro antioxidant activity.
We detail the first reported case of traumatic oil glands induced by wounding in eucalypts.
Histological examinations revealed the new phloem tissue formed in the two years following
green pruning in 5-year-old E. globulus to be largely composed of secretory cavities similar
in appearance to oil glands. Subsequent analysis of extracts by GC-MS confirmed the
presence of volatile terpenes and phenols. The total oil content determined for wound associated
phloem extracts was significantly higher (>50 times) than for healthy stem
phloem extracts.
Based on these chemical and morphological findings, we propose a reassessment of the
importance of wound wood in tree compartmentalization response for E. globulus and
E. nitens, particularly in comparison with other woody tree species.

Item Type: Thesis (PhD)
Keywords: Eucalyptus globulus, Eucalyptus, Eucalyptus
Copyright Holders: The Author
Copyright Information:

Copyright 2003 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, 2003. Includes bibliographical references

Date Deposited: 09 Dec 2014 00:08
Last Modified: 11 Mar 2016 05:54
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