Wound-induced changes in the chemistry of birch foliage and their ecological consequence
Wound-induced changes in the chemistry of birch foliage and their ecological consequence
The main aims of this thesis were to investigate wound-induced responses in birch foliage following insect attack, and determine the chemical basis of such responses. Two species of birch were studied, Betula pubescens and B. pendula. Laboratory based palatability experiments demonstrated that the acceptability of artificially damaged leaves to the larvae of a polyphagous moth Spodoptera littoralis was significantly reduced. A field leaf palatability experiment set up in early summer demonstrated that the natural community of insect herbivores grazed less frequently on previously damaged leaves, than undamaged leaves. When grazing did occur on previously damaged leaves the amount removed was significantly less than that from undamaged leaves. A survey of natural grazing damage levels incurred on B. pendula indicated that frequent movement away from feeding sites occurred, thus creating a wide dispersal of damage. The chemical analysis concentrated on the phenols. An assay was developed to estimate the concentration of proanthocyanidins complexed with leaf fibre polysaccharide chains. Quantitative analyses showed significant increases in the levels of soluble phenols and leaf fibre proanthocyanidins in damaged leaves compared with undamaged mature leaves. Naturally damaged leaves were found to have higher phenolic levels than artificially damaged leaves. However, young, undamaged leaves had the highest concentrations of soluble phenols, though the proanthocyanidin levels varied considerably in this leaf type. Qualitative changes in the types of soluble leaf phenols were also demonstrated following damage to leaves. An amylase-starch assay showed enzyme inhibition associated with leaf extracts. Aqueous leaf extracts from damaged leaves imposed the greater inhibition. The ecological implications of wound-induced responses are discussed. The highly reactive nature of the phenolic compounds recorded in damaged leaves suggests that they may be responsible for the antiphagant properties found. A hypothetical sequence of changes in leaf phenolics following damage is proposed which explains much of the chemical and ecological evidence.
University of Southampton
Silkstone, Beverley Edwin
1989
Silkstone, Beverley Edwin
Silkstone, Beverley Edwin
(1989)
Wound-induced changes in the chemistry of birch foliage and their ecological consequence.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The main aims of this thesis were to investigate wound-induced responses in birch foliage following insect attack, and determine the chemical basis of such responses. Two species of birch were studied, Betula pubescens and B. pendula. Laboratory based palatability experiments demonstrated that the acceptability of artificially damaged leaves to the larvae of a polyphagous moth Spodoptera littoralis was significantly reduced. A field leaf palatability experiment set up in early summer demonstrated that the natural community of insect herbivores grazed less frequently on previously damaged leaves, than undamaged leaves. When grazing did occur on previously damaged leaves the amount removed was significantly less than that from undamaged leaves. A survey of natural grazing damage levels incurred on B. pendula indicated that frequent movement away from feeding sites occurred, thus creating a wide dispersal of damage. The chemical analysis concentrated on the phenols. An assay was developed to estimate the concentration of proanthocyanidins complexed with leaf fibre polysaccharide chains. Quantitative analyses showed significant increases in the levels of soluble phenols and leaf fibre proanthocyanidins in damaged leaves compared with undamaged mature leaves. Naturally damaged leaves were found to have higher phenolic levels than artificially damaged leaves. However, young, undamaged leaves had the highest concentrations of soluble phenols, though the proanthocyanidin levels varied considerably in this leaf type. Qualitative changes in the types of soluble leaf phenols were also demonstrated following damage to leaves. An amylase-starch assay showed enzyme inhibition associated with leaf extracts. Aqueous leaf extracts from damaged leaves imposed the greater inhibition. The ecological implications of wound-induced responses are discussed. The highly reactive nature of the phenolic compounds recorded in damaged leaves suggests that they may be responsible for the antiphagant properties found. A hypothetical sequence of changes in leaf phenolics following damage is proposed which explains much of the chemical and ecological evidence.
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Published date: 1989
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Local EPrints ID: 461106
URI: http://eprints.soton.ac.uk/id/eprint/461106
PURE UUID: df904006-ec6a-4439-a970-b45091e56f28
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Date deposited: 04 Jul 2022 18:35
Last modified: 04 Jul 2022 18:35
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Author:
Beverley Edwin Silkstone
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