Concentrations Of Phenolic Glycosides Research Articles

Consequences of clonal variation in aspen phytochemistry for late season folivores

This research was conducted to assess variation in the phytochemistry of aspen (Populus tremuloides Michaux) clones and its impact on two summer-feeding insect species: Canadian tiger swallowtails (Papilio canadensis Rothschild & Jordan) and big poplar sphinx moths (Pachysphinx modesta Harris). Eight aspen clones were established from root cuttings collected in the field and grown for two years in a common garden. Leaf tissues were assayed for water, nitrogen, total nonstructural carbohydrates, condensed tannins, and phenolic glycosides. Both long- and short-term feeding trials were conducted to evaluate the effects of foliage quality on insect performance. Chemical analyses showed that concentrations of phytochemicals varied significantly among aspen clones, and that such variation was greater for secondary metabolites than for primary metabolites. Performance of both insect species varied among aspen clones and was negatively correlated with foliar phenolic glycoside concentrations. Comparison of results from this and an earlier study with the same plants indicates that genetic factors influence both clonal variation in secondary chemistry and phenological expression of such variation through time.

Influence of Pulp and Paper Mill Wastewater on Chrysomela scripta (Coleoptera: Chrysomelidae) Performance and Populus Plant Traits

The effect of wastewater irrigation on resistance of poplar trees to the cottonwood leaf beetle, Chrysomela scripta F., was investigated. Five Populus clones were tested in a greenhouse for their effects on the survival, fresh pupal weight, and development time (from egg to adult) of the cottonwood leaf beetle when they were irrigated with either wastewater or freshwater. Foliar concentrations of nitrogen, mineral elements (P, Mn, Mg, Ca, Na, K), phenolic glycosides, and leaf toughness also were measured to understand the potential mechanisms of resistance to the cottonwood leaf beetle. C. scripta performance was negatively affected by irrigation with wastewater; both survival and pupal weight were reduced. Performance also varied among clones and was the worst on Populus fremontii Watson variety wislenzensii , a native species. Leaf toughness and foliar N level were not affected by the irrigation treatment and were not correlated with larval growth and survival. Among minerals, foliar concentrations of sodium increased with wastewater irrigation, and were related negatively to pupal weights. Foliar magnesium also was influenced by the irrigation treatment but it was not correlated with C. scripta performance. Manganese varied with clone, but not with the type of water used for irrigation, and was correlated negatively with survival and related positively to development time. Differences in phenolic glycosides were observed between treatments and among clones, but there were no detectable relationships between phenolic glycosides and C. scripta performance.

Clonal variation in foliar chemistry of aspen: effects on gypsy moths and forest tent caterpillars.

Quaking aspen (Populus tremuloides) exhibits striking intraspecific variation in concentrations of phenolic glycosides, compounds that play important roles in mediating interactions with herbivorous insects. This research was conducted to assess the contribution of genetic variation to overall phenotypic variation in aspen chemistry and interactions with gypsy moths (Lymantria dispar) and forest tent caterpillars (Malacosoma disstria). Thirteen aspen clones were propagated from field-collected root material. Insect performance assays, measuring survival, development, growth, and food utilization indices, were conducted with second and/or fourth instars. Leaf samples were assayed for water, nitrogen, total nonstructural carbohydrates, condensed tannins, and phenolic glycosides. Results showed substantial among-clone variation in the performance of both insect species. Chemical analyses revealed significant among-clone variation in all foliar constituents and that variation in allelochemical contents differed more than variation in primary metabolites. Regression analyses indicated that phenolic glycosides were the dominant factor responsible for among-clone variation in insect performance. We also found significant genetic trade-offs between growth and defense among aspen clones. Our results suggest that genetic factors are likely responsible for much of the tremendous phenotypic variation in secondary chemistry exhibited by aspen, and that the genetic structure of aspen populations may play important roles in the evolution of interactions with phytophagous insects.

CO2‐mediated changes in aspen chemistry: effects on gypsy moth performance and susceptibility to virus

We investigated the effects of long‐term CO2 enrichment on foliar chemistry of quaking aspen (Populus tremuloides) and the consequences of chemical changes for performance of the gypsy moth (Lymantria dispar) and susceptibility of the gypsy moth to a nucleopolyhedrosis virus (NPV). Foliage was collected from outdoor open‐top chambers and fed to insects in a quarantine rearing facility. Under enriched CO2, levels of leaf nitrogen declined marginally, levels of starch and phenolic glycosides did not change, and levels of condensed tannins increased. Long‐term bioassays revealed reduced growth (especially females), prolonged development and increased consumption in larvae fed high‐CO2 foliage but no significant differences in final pupal weights or female fecundity. Short‐term bioassays showed weaker, and sex‐specific, effects of CO2 treatment on larval performance. Correlation analyses revealed strong, negative associations between insect performance and phenolic glycoside concentrations, independent of CO2 treatment. Larval susceptibility to NPV did not differ between CO2 treatments, suggesting that effects of this natural enemy on gypsy moths are buffered from CO2‐induced changes in foliar chemistry. Our results emphasize that the impact of enriched CO2 on plant–insect interactions will be determined not only by how concentrations of plant compounds are altered, but also by the relevance of particular compounds for insect fitness. This work also underscores the need for studies of genetic variation in plant responses to enriched CO2 and long‐term population‐level responses of insects to CO2‐induced changes in host quality.

The Genetic Basis for Variation in the Concentration of Phenolic Glycosides in Salix sericea: an Analysis of Heritability

The Genetic Basis for Variation in the Concentration of Phenolic Glycosides in Salix sericea: an Analysis of Heritability

The genetic basis for variation in the concentration of phenolic glycosides in Salix sericea: an analysis of heritability

Willows and many other members of the Salicaceae often produce phenolic glycosides, and the concentrations of these are known to vary among plants. We used progeny from a factorial half-sib quantitative genetics experiment with Salix sericea to determine whether the concentration of two phenolic glycosides, salicortin and 2′-cinnamoylsalicortin, show additive heritability. We found that the concentration of salicortin was much higher than 2′-cinnamoylsalicortin, and that both compounds showed additive genetic variation. However, the heritability of these two chemicals differed dramatically. We obtained heritability values of 0.20 for salicortin and 0.59 for 2′-cinnamoylsalicortin. Plant growth parameters were not strongly correlated with the concentrations of these phenolic glycosides.

Preservation of salicaceae leaves for phytochemical analyses: Further assessment

The chemistry of the plant family Salicaceae has been of interest to researchers as diverse as chemical ecologists, chemosystematists, and paper chemists. Continuing the debate on proper methods for preservation of plant material prior to analysis, vacuum-drying was recently advocated, because freeze-drying may cause degradation of phenolic glycosides. This study was conducted to clarify the consequences of freeze-drying for foliar secondary chemicals and to evaluate the consequences of vacuum-drying for primary compounds (protein and carbohydrates). Leaves of quaking aspen (Populus tremuloides) were flash-frozen in liquid nitrogen and freeze-dried or vacuum-dried at room temperature. We then analyzed samples for levels of salicortin and tremulacin (phenolic glycosides), condensed tannins, nitrogen, soluble protein, sugars, and starch. Freeze-drying did not alter the concentrations of phenolic glycosides or tannins, relative to vacuum-drying. Freeze-drying did cause a small and inexplicable decline in nitrogen and soluble protein. Vacuum-drying, however, reduced starch concentrations by 38%. We suggest that the vacuum-drying method be used in studies in which carbohydrates are of no interest. For studies measuring carbohydrates, however, freeze-drying is a better alternative, and should effect no changes in levels of secondary compounds if samples are not allowed to thaw during the drying process.

Preserving leaves for tannin and phenolic glycoside analyses: A comparison of methods using three willow taxa

Members of the Salicaceae often produce phenolic glycosides and condensed tannins. There is much debate on the best method for the preservation of leaf material prior to chemical analysis. Published results indicate freeze-drying, a method commonly used for tannin analysis, may be inappropriate for phenolic glycosides, unless done in a manner to prevent thawing during the drying process. Another commonly employed method, air-drying, is appropriate for phenolic glycosides but inappropriate for condensed tannins. I present evidence using willow leaves that demonstrates that: (1) leaves freeze-dried in external flasks without temperature control contain lower concentrations of phenolic glycosides (salicortin and 2'-cinnamoylsalicortin), (2) air-dried leaves have reduced concentrations of condensed tannins, while (3) vacuum-dried fresh leaves have high concentrations of both phenolic glycosides and condensed tannins. Freeze-drying caused salicortin and 2'-cinnamoyl salicortin concentrations to drop by 20 mg/g and 4 mg/g, respectively. Salicin, a product of salicortin and 2'-cinnamoyl salicortin degradation, is absent in vacuum-dried leaves, present in air-dried leaves and very high in freeze-dried leaves. Thus, the presence of salicin in this system is an artifact of the preservation technique. Condensed tannin concentrations dropped nearly 20 mg/g when leaves were air-dried. Thus, vacuum-drying fresh leaves allows researchers to quantify phenolic glycosides and condensed tannins from the same leaf material.

Intraspecific variation in aspen phytochemistry: effects on performance of gypsy moths and forest tent caterpillars.

Individual quaking aspen trees vary greatly in foliar chemistry and susceptibility to defoliation by gypsy moths and forest tent caterpillars. To relate performance of these insects to differences in foliar chemistry, we reared larvac from egg hatch to pupation on leaves from different aspen trees and analyzed leaf samples for water, nitrogen, total nonstructural carbohydrates, phenolic glycosides, and condensed tannins. Larval performance varied markedly among trees. Pupal weights of both species were strongly and inversely related to phenolic glycoside concentrations. In addition, gypsy moth performance was positively related to condensed tannin concentrations, whereas forest tent caterpillar pupal weights were positively associated with leaf nitrogen concentrations. A subsequent study with larvae fed aspen leaves supplemented with the phenolic glycoside tremulacin confirmed that the compound reduces larval performance. Larvae exhibited increased stadium durations and decreased relative growth rates and food conversion efficiencies as dietary levels of tremulacin increased. Differences in performance were more pronounced for gypsy moths than for forest tent caterpillars. These results suggest that intraspecific variation in defensive chemistry may strongly mediate interactions between aspen, gypsy moths and forest tent caterpillars in the Great Lakes region, and may account for differential defoliation of aspen by these two insect species.

The genetic basis for variation in the concentration of phenolic glycosides in Salix sericea: Clonal variation and sex-based differences

Many members of the Salicaceae produce phenolic glycosides, and the concentrations of these are known to vary among plants. We determined whether the concentration of two phenolic glycosides, salicortin and 2′-cinnamoyl salicortin, varied among clones of Salix sericea and whether this variation was due to the sex of the plant. We tested 16 clones, seven male and nine female, for variation in glycoside concentration and several plant growth rate parameters. The concentrations of salicortin and 2′-cinnamoyl salicortin varied extensively between clones and exhibited broad-sense heritability. Clones also varied in growth rate. Interestingly, none of these clone effects were due to differences between male and female plants. There was no correlation between shoot length and chemistry, although it appears that faster growing clones often produce lower concentrations of the two phenolic glycosides. We discuss these findings in relation to current theory concerning plant allocation to growth and defense.

Occurrence and performance of the aspen blotch miner, Phyllonorycter salicifoliella, on three host-tree species.

Larvae of the aspen blotch miner, Phyllonorycter salicifoliella Chambers (Lepidoptera: Gracillariidae), feed within leaves of three host-tree species in north-central Minnesota, USA. Far more individuals occur on Populus tremuloides than on P. balsamifera or P. grandidentata. We tested whether this pattern of host use reflected variable performance among alternative hosts by examining survivorship, sources of mortality, pupal mass, feeding efficiency, and development time of miners on each tree species. We also determined foliar water, nitrogen, condensed tannin, and phenolic glycoside content of host trees to test if host-tree chemical attributes were responsible for differences in performance. There was no significant difference in egg-to-adult survival among miners on different hosts, although dominant sources of mortality did vary. Miners on P. grandidentata suffered less parasitism and more predation than those on the other hosts, even though most parasitoid species attacked miners on all hosts. The other performance parameters varied among host species, but not in a consistent pattern. Pupal mass was greatest on P. tremuloides and P. balsamifera, the hosts with comparatively high foliar nitrogen and low phenolic glycoside concentrations. However, feeding efficiency was greatest and development time shortest for miners on P. grandidentata. Thus, pupal mass was the only index of performance maximized on P. tremuloides, the most commonly used host. Infrequent occurrence of Phyllonorycter salicifoliella on P. grandidentata results in part from phenological differences between this and the other host species. Low oviposition rates on P. balsamifera are correlated with low abundance of this host at the study site and a phenolic glycoside profile different from that of the other host species.

Chemical analysis of phenolic glycosides: art, facts, and artifacts.

Phenolic glycosides have been the subject of considerable interest in recent ecological and systematic studies, especially those involving the Salicaceae. But these compounds are markedly labile in aqueous media, and the consequences of spontaneous degradation for valid interpretation of results have been largely ignored by researchers. We found that freeze-drying and oven-drying of leaf samples from several Populus and Salix species produced dramatic changes in the total and relative concentrations of specific phenolic glycosides, when compared to analyses of fresh material. Extraction in aqueous and alcoholic media for extended (24 h) periods also effected changes in glycoside concentrations. Alterations in phenolic glycoside concentrations, interconversions among glycosides, and production of artifactual glycosides result from a series of hydrolytic reactions. These deleterious effects can be best (but not entirely) avoided by the use of fresh plant material, cold, nonaqueous extraction solvents, and short extraction times. Because individual phenolic glycosides exhibit very different biological activities against herbivores, we caution ecologists to use utmost care in the performance and interpretation of phenolic glycoside assays.

Effect of nitrogen fertilization upon the secondary chemistry and nutritional value of quaking aspen (Populus tremuloides Michx.) leaves for the large aspen tortrix (Choristoneura conflictana (Walker)).

We investigated the effects of nitrogen fertilization upon the concentrations of nitrogen, condensed tannin and phenolic glycosides of young quaking aspen (Populus tremuloides) leaves and the quality of these leaves as food for larvae of the large aspen tortrix (Choristoneura conflictana), a Lepidopteran that periodically defoliates quaking aspen growing in North America. Nitrogen fertilization resulted in decreased concentrations of condensed tannin and phenolic glycosides in aspen leaves and an increase in their nitrogen concentration and value as food for the large aspen tortrix. These results indicate that plant carbon/nutrient balance influences the quality of aspen leaves as food for the large aspen tortrix in two ways, by increasing the concentrations of positive factors (e.g. nitrogen) and decreasing the concentrations of negative factors (eg. carbon-based secondary metabolites) in leaves. Addition of purified aspen leaf condensed tannin and a methanol extract of young aspen leaves that contained condensed tannin and phenolic glycosides to artificial diets at high and low levels of dietary nitrogen supported this hypothesis. Increasing dietary nitrogen increased larval growth whereas increasing the concentrations of condensed tannin and phenolic glycosides decreased growth. Additionally, the methanol extract prevented pupation. These results indicate that future studies of woody plant/insect defoliator interactions must consider plant carbon/nutrient balance as a potentially important control over the nutritional value of foliage for insect herbivores.

Phenolic compounds of willow bark as deterrents against feeding by mountain hare.

Overwintering mountain hares (Lepus timidus) fed selectively on the shoots of a number of northern willow (Salix spp.) species. The hares preferred certain species over others and mature shoots over juvenile ones. There was a negative correlation between the phenolic glycoside concentration in the twigs and the hares' feeding. This correlation was substantiated by feeding experiments in which oat grains treated with purified phenoglycoside and catechin fractions of willow bark were offered along with untreated control oat grains to free-ranging mountain hares. Both fractions in concentrations normally found in willow twigs inhibited hare feeding. The results suggest that these phenolic compounds play a crucial role in the building up of resistance patterns among the willows. The decline in resistance in mature shoots of tall willows indicates that the juvenile resistance can be, perhaps secondarily, an adaptation against mammals browsing from ground level. Accordingly, low willow species retain a high level of resistance also in maturity.

A Reevaluation of the Taxonomy of Salix tyrrellii, a Sand Dune Endemic

Salix tyrrellii is an endemic taxon described from the active sand dunes south of Lake Athabasca, Saskatchewan. It is related to S. planifolia from which it differs in having slender erect branches which are often slightly tortuose, a pro- longed juvenile growth form, smaller and thicker leaves with stomata on both sur- faces and low concentrations of phenolic glycosides in bark tissues. Its amphisto- matous leaves link this taxon to some arctic populations of S. planifolia in the N.W.T. and Manitoba which may be ancestral to it. The growth form of S. tyrrellii is probably an adaptation to active sand dune habitats. Phenolic glycosides may play a role in its adaptation to active sand dunes. Because of its close relationship to S. planifolia, the new combination S. planifolia ssp. tyrreliji (Raup) Argus is proposed. An extensive system of active sand dunes lies along the south shore of Lake Athabasca in northwestern Saskatchewan and adjacent Alberta. Large dune fields covering 300 sq km and 30 sq km are located near the mouths of the William and MacFarlane Rivers, respectively. The region of actively blowing sand extends over 90 km along the lake shore and up to 20 km inland (Map 1). The dune fields consist of loose sand, some of which is blown into dunes up to 35 m tall, overlying gravel pavements and sandy glacio-fluvial materials. Smaller dunes scattered throughout the region are parabola dunes that have developed from blowouts in the sandy Pinus banksiana and Picea mariana forests that stabilize much of the sand area. The active sand habitat supports a distinctive flora made up of an unusually large number of endemic taxa together with disjunct arctic species and the more common boreal and northern Great Plains species.