Metabolic modifications of birch leaf phenolics by an herbivorous insect: detoxification of flavonoid aglycones via glycosylation.

The metabolic modifications of birch (Betula pubescens Ehrh.) leaf phenolics in the digestive tract of its major defoliator, larvae of the autumnal moth Epirrita autumnata, were studied. The main phenolic acids of birch, i.

Foliar oxidases as mediators of the rapidly induced resistance of mountain birch against Epirrita autumnata.

Induced resistance of the mountain birch against its main defoliator Epirrita autumnata is a well-characterized phenomenon. The causal mechanism for this induced deterioration, however, has not been unequivocally explained, and no individual compound or group of traditional defensive compounds has been shown to explain the phenomenon. Phenolic compounds are the main secondary metabolites in mountain birch leaves, and the biological activity of phenolics usually depends on their oxidation.

Foliar phenolics are differently associated with Epirrita autumnata growth and immunocompetence.

The quality of available food may affect insect herbivores directly (via growth and survivorship) and/or indirectly (by modifying insect vulnerability to parasitoids and pathogens). We examined the relationship between different phenolic compounds, belonging to various phenolic groups, in Betula pubescens spp. czerepanovii (mountain birch) foliage and the larval performance of the geometrid Epirrita autumnata (autumnal moth).

Quantitative analysis of polymeric proanthocyanidins in birch leaves with normal-phase HPLC.

The proanthocyanidin composition and content in the leaves of nine birch species (Betula albosinensis, B. ermanii B. maximowicziana, B.

Defoliating insect immune defense interacts with induced plant defense during a population outbreak.

During population outbreaks, top-down and bottom-up factors are unable to control defoliator numbers. To our knowledge, details of biotic interactions leading to increased population density have not been studied during real population outbreaks. We experimentally assessed the strength of plant defenses and of insect immunocompetence, assumed to contribute to active insect resistance against parasitoids and pathogens, in the geometrid Epirrita autumnata during a steep increase in population density.

Delayed induced responses of birch glandular trichomes and leaf surface lipophilic compounds to mechanical defoliation and simulated winter browsing.

Changes in morphology and chemistry of leaf surface in response to herbivore damage may increase plant resistance to subsequent herbivore attack; however, there is lack of studies on induced responses of glandular trichomes and their exudates in woody plants and on effects of these changes on herbivores. We studied delayed induced responses in leaf surface traits of five clones of silver birch (Betula pendula Roth) subjected to various types of mechanical defoliation and simulated winter browsing. Glandular trichome density and concentrations of the majority of surface lipophilic compounds increased in trees defoliated during the previous summer.

Defensive effect of surface flavonoid aglycones of Betula pubescens leaves against first instar Epirrita autumnata larvae.

The surface of birch leaves contains glandular trichomes that secrete exudates containing flavonoid aglycones. We investigated the biological activities of white birch (Betula pubescens) leaf surface exudates against larvae of the autumnal moth, Epirrita autumnata, a common insect pest of birch. We found that tree-specific mortality (up to 100%) of first instar larvae correlated strongly with the tree-specific contents of surface flavonoid aglycones (r(s) = 0.

Rapid herbivore-induced changes in mountain birch phenolics and nutritive compounds and their effects on performance of the major defoliator, Epirrita autumnata.

Insect damage changes plant physiology and chemistry, and such changes may influence the performance of herbivores. We introduced larvae of the autumnal moth (Epirrita autumnata Borkh.) on individual branches of its main host plant.

Root versus canopy uptake of heavy metals by birch in an industrially polluted area: contrasting behaviour of nickel and copper.

We investigated root versus canopy uptake of nickel and copper by mountain birch, Betula pubescens subsp. czerepanovi, close to a nickel-copper smelter on the Kola Peninsula, northwest Russia. To distinguish between aerial contamination of leaf surfaces by dust particles and root-derived contamination of leaves by soluble metals, we transplanted seedlings from a control site to clean and metal-contaminated soils and exposed these seedlings both in clean and polluted sites.

Insect performance on experimentally stressed woody plants: a meta-analysis.

In this review, we test the hypothesis that abiotic stress increases the suitability of plants as food for herbivores. We conducted a meta-analysis that included 70 experimental studies in which insect performance was measured on woody plants subjected to water stress, pollution, and/or shading. Overall, plant stress had no significant effect on insect growth rate, fecundity, survival, or colonization density.

Putting the insect into the birch-insect interaction.

Leaf maturation in mountain birch (Betula pubescens ssp. czerepanovii) is characterized by rapid shifts in the types of dominant phenolics: from carbon-economic flavonoids aglycons in flushing leaves, via hydrolysable tannins and flavonoid glycosides, to carbon-rich proanthocyanidins (condensed tannins) in mature foliage. This shift accords with the suggested trade-offs between carbon allocation to plant defense and growth, but may also relate to the simultaneous decline in nutritive leaf traits, such as water, proteins and sugars, which potentially limit insect growth.

Seasonal changes in birch leaf chemistry: are there trade-offs between leaf growth and accumulation of phenolics?

Several plant-herbivore hypotheses are based on the assumption that plants cannot simultaneously allocate resources to growth and defence. We studied seasonal patterns in allocation to growth and putatively defensive compounds by monitoring several chemical and physical traits in the leaves of mountain birch from early June (budburst) to late September (leaf senescence). We found significant seasonal changes in all measured characteristics, both in terms of concentrations (mg g) and amounts (mg leaf).

Seasonally varying diet quality and the quantitative genetics of development time and body size in birch feeding insects.

Genetic variance-covariance structures (G), describing genetic constraints on microevolutionary changes of populations, have a central role in the current theories of life-history evolution. However, the evolution of Gs in natural environments has been poorly documented. Resource quality and quantity for many animals and plants vary seasonally, which may shape genetic architectures of their life histories.

Proanthocyanidins of mountain birch leaves: quantification and properties.

Proanthocyanidins (PAs; condensed tannins) are present in mountain birch leaves in soluble and cell wall-bound forms. Crude preparations of soluble PAs were isolated from birch leaves and purified by chromatography on a Sephadex LH-20 column with a yield of about 7% of leaf dry mass. Some chemical characteristics were elucidated with 13C-NMR and HPLC-ECI-MS.

Patterns in content of phenolic compounds in leaves of mountain birches along a strong pollution gradient.

The contents of individual low-molecular weight phenolic compounds (LMWPs) in mountain birch, Betula pubescens ssp. czerepanovii, leaves collected during 1996-1998 in six plots 7-65 km south of the nickel-copper smelter at Monchegorsk, Kola Peninsula, NW Russia, were reported. A high-performance liquid chromatography-electrospray ionisation-mass spectrometry (HPLC-ESI-MS) was used for the rapid identification of low-molecular weight phenolics.

Seasonal variation in the content of hydrolysable tannins in leaves of Betula pubescens.

The contents of 13 hydrolysable tannins in the leaves of white birch (Betula pubescens L.) trees were analysed at twelve stages throughout the growing season. All individual galloylglucoses, from 1-O-galloyl-beta-D-glucopyranose to 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranose, accumulated in young leaves, while ellagitannins showed significantly variable seasonal trends.

Phenolic and phenolic-related factors as determinants of suitability of mountain birch leaves to an herbivorous insect.

We investigated the role of phenolic and phenolic-related traits of the leaves of mountain birch (Betula pubescens ssp. czerepanovii) as determinants of their suitability for the growth of larvae of the geometrid Epirrita autumnata. As parameters of leaf suitability, we determined the contents of total phenolics, gallotannins, soluble and cell-wall-bound proanthocyanidins (PAS and PAB, respectively), lignin, protein precipitation capacity of tannins (PPC), and leaf toughness.

Characterisation of hydrolysable tannins from leaves of Betula pubescens by high-performance liquid chromatography-mass spectrometry.

A high-performance liquid chromatography-electrospray ionisation mass spectrometry (HPLC-ESI-MS) method, assisted by diode array detection, for the characterisation of individual hydrolysable tannins in birch leaves was developed. With the method, it was found that birch (Betula pubescens) leaves contained an exceptionally complex mixture of hydrolysable tannins; 14 gallotannins and 20 ellagitannins were identified. The developed HPLC-ESI-MS method allows the qualitative and quantitative determination of individual gallotannins and ellagitannins directly from crude birch leaf extract.

Covariation of fluctuating asymmetry, herbivory and chemistry during birch leaf expansion.

Fluctuating asymmetry (FA) is used to describe developmental instability in bilateral structures. In trees, high FA of leaves has been assumed to indicate the level of environmental or genetic stress, and for herbivores leaves from such trees have been shown to be in some cases (though not invariably) of higher quality compared to trees with symmetrical leaves. We demonstrated that FA of birch leaves correlated positively with growth rate of leaves, and with the amount of leaf biomass consumed by larvae of the geometrid Epirrita autumnata.

Multiplicity of biochemical factors determining quality of growing birch leaves.

Due to rapidly changing physical and biochemical characteristics of growing leaves, correlations between traits of foliage biochemistry and the performance indices of flush feeding herbivores may vary considerably following relatively minor changes in experimental conditions. We examined the effects of the seasonal and inter-tree variation of a comprehensive array of biochemical compounds on the success of an early season geometrid, Epirrita autumnata, feeding on maturing foliage of mountain birch, Betula pubescens ssp. czerepanovii.

Delayed induced changes in the biochemical composition of host plant leaves during an insect outbreak.

In birch, Betula pubescens, herbivore-induced delayed induced resistance (DIR) of defoliated trees may cause a strong reduction in the potential fecundity of a geometrid folivore Epirrita autumnata. In this study, we examined the biochemical basis of DIR in birch leaves during a natural outbreak of E. autumnata.

Delayed induced resistance and increase in leaf fluctuating asymmetry as responses of Salix borealis to insect herbivory.

An outbreak of leaf beetle Melasoma lapponica in two localities around the Severonikel smelter in Kola Peninsula, north-west Russia, resulted in severe defoliation of Salix borealis, observed for the first time in August 1993 and then again in 1994 and 1995. Before the first severe defoliation, in July 1993, performance of M. lapponica larvae in plots with a high beetle density was either better or the same as in low-density plots.

Antioxidant responses to simulated acid rain and heavy metal deposition in birch seedlings.

This study measured the responses of different anti-oxidants in 2-year-old birch (Betula pendula Roth) seedlings subjected to simulated acid rain (pH 4.0) and heavy metals (Cu/Ni), applied alone or in combination for 2 months. The applied concentrations of pollutants did not significantly affect seedling biomass or total glutathione levels.