Early lateral root formation in response to calcium and nickel shows variation within disjunct populations of Arabidopsis lyrata spp. lyrata.

Root architecture is important in nutrient uptake and avoidance of toxic compounds within the soil. Arabidopsis lyrata spp. lyrata has widespread distribution in disjunct environments that encounter unique stressors starting at germination. Five populations of A. lyrata spp. lyrata show local adaptation to Nickel (Ni) but cross-tolerance to variations in Calcium (Ca) concentration within the soil. Differentiation among the populations begins early in development and appears to impact timing of lateral root formation; therefore the purpose of the study was to understand changes in root architecture and root exploration in response to Ca and Ni within the first three weeks of growth. Lateral root formation was first characterized under one concentration of Ca and Ni. Lateral root formation and tap root length were reduced in all five populations in response to Ni compared to Ca, with the least reduction in the three serpentine populations. When the populations were exposed to a gradient (either Ca or Ni) there were differences in population response based on the nature of the gradient. Start side was the greatest determinant of root exploration and lateral root formation under a Ca gradient, while population was the greatest determinant of root exploration and lateral root formation under a Ni gradient. All populations exhibited about the same frequency of root exploration under a Ca gradient, while the serpentine populations exhibited much higher levels of root exploration under a Ni gradient compared to the two non-serpentine populations. Differences among populations in response to Ca and Ni demonstrate the importance of stress responses early in development, particularly in species that have widespread distribution among disparate habitats.

Woody plant secondary chemicals increase in response to abundant deer and arrival of invasive plants in suburban forests.

Plants in suburban forests of eastern North America face the dual stressors of high white-tailed deer density and invasion by nonindigenous plants. Chronic deer herbivory combined with strong competition from invasive plants could alter a plant's stress- and defense-related secondary chemistry, especially for long-lived juvenile trees in the understory, but this has not been studied. We measured foliar total antioxidants, phenolics, and flavonoids in juveniles of two native trees, Fraxinus pennsylvanica (green ash) and Fagus grandifolia (American beech), growing in six forests in the suburban landscape of central New Jersey, USA. The trees grew in experimental plots subjected for 2.5 years to factorial treatments of deer access/exclosure × addition/no addition of the nonindigenous invasive grass Microstegium vimineum (Japanese stiltgrass). As other hypothesized drivers of plant secondary chemistry, we also measured nonstiltgrass herb layer cover, light levels, and water availability. Univariate mixed model analysis of the deer and stiltgrass effects and multivariate structural equation modeling (SEM) of all variables showed that both greater stiltgrass cover and greater deer pressure induced antioxidants, phenolics, and flavonoids, with some variation between species. Deer were generally the stronger factor, and stiltgrass effects were most apparent at high stiltgrass density. SEM also revealed that soil dryness directly increased the chemicals; deer had additional positive, but indirect, effects via influence on the soil; in beech photosynthetically active radiation (PAR) positively affected flavonoids; and herb layer cover had no effect. Juvenile trees' chemical defense/stress responses to deer and invasive plants can be protective, but also could have a physiological cost, with negative consequences for recruitment to the canopy. Ecological implications for species and their communities will depend on costs and benefits of stress/defense chemistry in the specific environmental context, particularly with respect to invasive plant competitiveness, extent of invasion, local deer density, and deer browse preferences.

Screening for consistency and contamination within and between bottles of 29 herbal supplements.

In the United States the marketing of dietary supplements, of which the majority are herbal supplements, is currently a multibillion-dollar industry involving use from over half of the adult population. Due to their frequency of use and the lack of regulation of herbal supplements by the Food and Drug Administration (FDA) it is important for the health and safety of consumers to know about consistency of supplements and any possible contamination by harmful products, such as heavy metals or microorganisms. The purpose of the study was to determine consistency and contamination within and between bottles of common herbal supplements. Duplicate bottles of 29 herbal supplements were tested for consistency for antioxidant activity, phenolic concentration and flavonoid concentration under methanolic and water extraction. The supplements were also analyzed for the presence of metals and fungal contaminants. For all of the supplements tested there was high variability around the mean in antioxidant activity, phenolic concentrations and flavonoid concentrations, with coefficients of variation (CV) ranging from 0-120. Zinc was found in almost 90% of the supplements, nickel in about half of the supplements and lead in none of the supplements. Approximately 60% of the supplements contained fungal isolates. Although the majority of the fungi that were found in the supplements are generally not hazardous to human health, many of them could be problematic to sensitive groups, such as immunocompromised individuals. The data, which demonstrates contamination and a lack of consistency, in conjunction with previous studies on supplement contamination, strengthen the case that the FDA should regulate over-the-counter herbal supplements the same way that they regulate food and drugs. Until such time it is crucial that consumers are informed that many of the supplements that they take may lack the standardization that would reduce the chance of contamination and lead to consistency from one pill to the next.

Evidence for cross-tolerance to nutrient deficiency in three disjunct populations of Arabidopsis lyrata ssp. lyrata in response to substrate calcium to magnesium ratio.

Species with widespread distributions that grow in varied habitats may consist of ecotypes adapted to a particular habitat, or may exhibit cross-tolerance that enables them to exploit a variety of habitats. Populations of Arabidopsis lyrata ssp. lyrata (L.) O'Kane & Al-Shehbaz grow in a wide variety of edaphic settings including serpentine soil, limestone sand, and alluvial flood plains. While all three of these environments share some stressors, a crucial difference among these environments is soil calcium to magnesium ratio, which ranges from 25:1 in the limestone sand to 0.2:1 in serpentine soil. The three populations found on these substrates were subjected to three different Ca to Mg ratios under controlled environmental conditions during germination and rosette growth. Response to Ca to Mg ratio was evaluated through germination success and radicle growth rate, rosette growth rate, and the content of Ca and Mg in the rosette. All three populations were particularly efficient in fueling growth under nutrient deficiency, with the highest nutrient efficiency ratio for Ca under Ca deficiency and for Mg under Mg deficiency. Although the serpentine population had significantly higher leaf Ca to Mg ratio than the limestone or flood plain populations under all three Ca to Mg ratios, this increase did not result in any advantage in growth or appearance of the serpentine plants, during early life stages before the onset of flowering, even in the high Mg substrate. The three populations showed no population by substrate interaction for any of the parameters measured indicating that these populations may have cross-tolerance to substrate Ca to Mg ratio.