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- Lundborg, Lina, 1986-, et al.
(författare)
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Conifer chemical defenses influence meal properties of the pine weevil Hylobius abietis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Chemical defenses of conifers can be experimentally activated to respond more efficiently to feeding damage by insects. One chemical elicitor that triggers plant defenses, and thereby protects conifers, is methyl jasmonate (MeJA). However, there is little known about the associations between MeJA-induced conifer defenses, and the meal properties of phytophagous insects. To address this knowledge gap, we have analyzed relations between volatile contents of Scots pine (Pinus sylvestris L.) tissues, and meal properties of the pine weevil (Hylobius abietis (L.)). Phloem and needles (both weevil target tissues) from MeJA-treated and control seedlings were extracted by n-hexane and analyzed by two-dimensional gas chromatography-mass spectrometry (2D GC-MS). Feeding of pine weevils on seedlings from the same batches were video-recorded to determine meal properties. Multivariate statistical analyses showed that phloem and needle contents of MeJA-treated seedlings had different volatile compositions from the control seedlings. Levels of (+)-α-pinene were high, and levels of the antifeedant 2-phenylethanol were low, in phloem of control seedlings with feeding damage. Accordingly, pine weevils fed more slowly and had shorter meals on MeJA-treated seedlings. In addition, the chemical compositions of phloem and needles – and accordingly weevil meal durations on them – were more similar in MeJA-treated seedlings than in controls. The results illustrate that detailed knowledge of insect responses can help efforts to identify and elucidate specific roles of resistance agents in complex chemical profiles.
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- Lundborg, Lina, 1986-, et al.
(författare)
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Constitutive and MeJA-induced terpenes in Pinus pinaster and Pinus radiata in relation to Hylobius abietis
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The feeding preference of the pine weevil to Maritime pine (Pinus pinaster Ait.) and Monterey pine (Pinus radiata D. Don) differ in laboratory tests and in the field: Can this be explained by the volatile compounds released by the seedlings? Understanding the interaction between the chemical defenses of young pines and feeding preferences of the pine weevil (Hylobius abietis (L.)) may improve protection methods of conifer seedlings in Europe and Asia. In order to increase the resistance of seedlings of P. pinaster and P. radiata, these were treated with the chemical elicitor methyl jasmonate (MeJA). The effects of the MeJA treatments on the amounts and composition of volatile terpenes in tissues (needles and phloem) were investigated by extracting these in hexane, whereafter the volatile constituents of the extracts were separated and identified by gas chromatography-mass spectrometry (GC-MS). In addition, the most abundant monoterpenes (α-pinene and β-pinene) were separated on a chiral column in their enantiomers. Already at the lowest concentration of MeJA treatment, 5 mM, the amounts of volatile terpenes in the needles of P. radiata increased and the seedling heights were reduced. In P. pinaster, on the other hand, no effect from the MeJA treatment was observed on the total volatile terpenes in the needles, and only at the strongest MeJA concentration, the seedling heights were affected. In the phloem of P. pinaster the composition of volatile contents, changed after MeJA treatment, showing a reduction in the (+)-α-pinene. In contrast, the amounts of (+)-α-pinene increased in P. radiata. In a previous study, controls and MeJA-treated pine seedlings, from the same MeJA treatment batches as in this study, were subjected to a field trial. In the field, the pine weevils preferred the seedlings of P. radiata over those of P. pinaster. We propose that the differences in induction of (+)-α-pinene may be important for explaining the differences in pine weevil feeding preferences.
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- Lundborg, Lina, 1986-, et al.
(författare)
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Methyl jasmonate-induced monoterpenes in Scots pine and Norway spruce tissues affect pine weevil orientation
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In large parts of Europe insecticide-free measures for protecting conifer plants are desired to suppress damage by the pine weevil Hylobius abietis (L.). Treatment with methyl jasmonate (MeJA), a chemical elicitor already used in crop production, may enhance expression of chemical defenses in seedlings in conifer regenerations. However, in a previous experiment MeJA treatment resulted in substantially better field protection for Scots pine (Pinus sylvestris L.) than for Norway spruce (Picea abies (L.) Karst.). Hypothesizing that the variations may be at least partly due to volatiles released by MeJA-treated seedlings and their effects on pine weevil orientation, we examined tissue extracts of seedlings (from the same batches as previously used) by two-dimensional GC-MS. We found that the MeJA treatment increased contents of the monoterpene (-)-β-pinene in phloem (the weevil’s main target tissue) of both tree species, however, the (-)-β-pinene/(-)-α-pinene ratio increased more in the phloem of P. sylvestris. We also tested the attractiveness of individual monoterpenes found in conifer tissues (needles and phloem) for pine weevils using an arena with traps baited with single-substance dispensers and pine twigs. Trap catches were reduced when the pine material was combined with a dispenser releasing (-)-β-pinene, (+)-3-carene, (-)-bornyl acetate or 1,8-cineole. However, (-)-α-pinene did not have this effect. Thus, the greater field protection of MeJA-treated P. sylvestris seedlings may be due to the selective induction of increases in contents of the deterrent (-)-β-pinene, in contrast to strong increases in both non-deterrent (-)-α-pinene and the deterrent (-)-β-pinene in P. abies seedlings.
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- Wang, Yan, 1987-, et al.
(författare)
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Hydration and dimensional stability of the intercalated galleries in xyloglucan/montmorillonite nanocomposites studied by molecular dynamics simulations
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The outstanding properties of biological composite nacre materials have for a long time inspired research and development of man-made bionanocomposites. One of the most recent nacre-mimetic bionanocomposites comprising xygloglucan (XG) and montmorillonite (Mnt) clay has been investigated by related model systems through Molecular dynamics (MD) simulations. The expansion of the inter-gallery of the XG-Mnt composites when exposed to water, has been found to be a key issue for the material property. In order to shed light on the mechanism for this swelling behavior we have investigated the relation between the hydration and the dimensional stability of the inter-gallery in XG-Mnt composites, exploring also the role of the dynamic state of the polymer XG for the dimensional change. We find that at a hydration level below 50%, XG-Mnt possesses good dimensional stability, suggesting a constant performance of the material, while at a hydration level of 75%, the expansion ratio of the composite is found to be slightly smaller than the swelling of Mnt clay. At the four-layer hydrate formation with a hydration level of 100%, the swelling ratios of clay and the2composite reach the same value, suggesting a critical point of losing dimensional stability. We conclude that the strong adhesion between the polymer XG and the Mnt clay is the main driving force for the preservation of the stability at lower hydration conditions, while the dynamics of the XG polymer is related to the losing of dimensional stability for the composite at higher hydration levels. The ramification of these results in terms of moisture sensitivity of the material is briefly discussed.
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- Wang, Yan, 1987-, et al.
(författare)
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Molecular mechanisms for the adhesion of chitin and chitosan to montmorillonite clay
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Molecular dynamics simulations have been performed to investigate molecular adhesion of chitin and chitosan oligomers to montmorillonite (Mnt) clay at different degrees of acetylation (DA, 0%, 20%, 40%, 60%, 80% and 100%) and different degree of protonation (DPr, 0%, 50%, 100% mimicking pH > 6.5, pH = 6.5, pH < 4, respectively) under fully hydrated conditions. Although the Mnt surface is negatively charged and a variation in DA also implies going from a positively charged oligomer at DA = 0% to a neutral oligomer at DA = 100%, the simulations show unexpectedly variation of the total molecular adhesion as a function of DA. From our analysis we propose that this quantitatively similar adhesion arise from two different mechanisms. At low DA, the oligomer is rich in positively charged amino groups interacting strongly with the negatively charged surface by direct electrostatic interaction. On the other hand, at high DA, electrically neutral acetyl groups are strongly correlated with the Na+ counter ions, which are in all cases stuck at the surface and the counter ions seem to act as ‘glue’ between the acetyl groups and the Mnt. However, when protonation was decreased, adhesion was significantly lowered. The reason is conclued by differences in charge distributions of the respective functional groups. A further investigation on the intramolecular hydrogen bonds formed in CHT or CHS shows that the adsorbed conformation of the polymer is also highly affected by DA. This work provides fundamental insights into adhesion mechanisms and is, of potential importance for the development of polymer-clay based composite materials.
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