Mercury accumulation and resistance to mercury stress in Rumex induratus and Marrubium vulgare grown in perlite

Plants of Rumex induratus and Marrubium vulgare, collected in the mining area of Almadén, were transferred to pots and grown for 2 months using perlite as substrate and treated with soluble mercury (Hg) in the applied nutrient solution. Mercury resistance, Hg bioaccumulation, and some stress biomarkers were investigated in both plant species. Mercury concentration increased in both plant species in response to Hg supply, but R. induratus was more effective in Hg accumulation. Rumex induratus and M. vulgare showed higher [Hg]_shoot‐to‐[Hg]_root ratios than other plant species. Mercury in the growth medium perlite was also investigated, distinguishing soluble, available, and total amounts of Hg in the medium. At the lower doses, one half of the applied Hg was retained by perlite. Rumex induratus decreased the available Hg fraction in perlite more than M. vulgare. The bioaccumulation factor ([Hg]_plant/[Hg]_available) was similar in both species and similar as found in previous field studies. Plant growth, water content, and chlorophyll concentration, and nutrient translocation were reduced in both plant species by the Hg. Rumex induratus showed higher resistance and Hg‐accumulation capacity than M. vulgare, due to the accumulation of thiols in roots and the absence of a lipid oxidative response.     

Determining the Validity of using Summer Monitoring to Estimate Annual Deposition of Acidic Pollutants in Southern Ontario,Canada

We tested the hypothesis that compensatory fertilization of Scots pine (Pinus sylvestris L.) stands polluted by theHarjavalta copper-nickel smelter in SW Finland alleviates thestress imposed by metal-contaminated soils. The treatments inthe experiment consisted of control, liming, slow-release mineral mixture and stand-specific fertilization, which comprised at least methylene urea and ammonium nitrate. Stresswas assessed by needle fluctuating asymmetry (FA) which increases with an increase in developmental instability. Sevenyears after the treatments, we found pronounced variation inboth FA and needle length among study sites (0.5, 2, 4 and 8 km from the smelter) and among treatments. FA increased and needlelength decreased with proximity to the pollution source. Variation in FA was independent of tree size (used as index ofgrowth rate in even-age stand); the effects of the treatmentson needle length, on the other hand, were expressed only inmedium-sized and large trees. Liming best alleviated pollutionstress, while the application of a slow-release mineral mixtureincreased FA by 30%. In pollution-stressed stands FA correlatedpositively with constitutive resin flow but was independent of volume growth. Our findings suggest that physiological stress (indicated by increase in developmental instability) and tree growth or stand productivity are not directly linked to one another, and that some increase in productivity can be achievedwithout the alleviation of pollution-induced stress.     

An attempt to recover the Po'ouli by translocation and an appraisal of recovery strategy for bird species of extreme rarity

The Po'ouli (Melamprosops phaeosoma), a Hawaiian honeycreeper endemic to Maui, has a population of only three known individuals; no breeding pair currently exists, and their home ranges are too far apart for breeding to occur. Without timely intervention this monotypic genus will likely go extinct. Conservationists have faced a dilemma: facilitate breeding amongst the known individuals, manage their ecosystem to benefit uncounted Po'ouli, or a combination of both? Po'ouli biology is poorly known - but their remote home ranges are closely monitored. A State and Federal Environmental Assessment in 1999 recommended that one Po'ouli be translocated into the home range of another in an attempt to facilitate breeding. This first manipulative recovery action was achieved in April 2002, and provided valuable new information for future captive management efforts, but upon release, radio telemetry confirmed that the translocated bird returned to its own home range after one day. We describe the recent progress that has been made to recover the Po'ouli, and critically evaluate the Po'ouli case study and the lessons learned from it that can help expedite recovery of other birds of extreme rarity.     

MESSENGER observations of the composition of Mercury's ionized exosphere and plasma environment

The region around Mercury is filled with ions that originate from interactions of the solar wind with Mercury's space environment and through ionization of its exosphere. The MESSENGER spacecraft's observations of Mercury's ionized exosphere during its first flyby yielded Na+, O+, and K+ abundances, consistent with expectations from observations of neutral species. There are increases in ions at a mass per charge (m/q) = 32 to 35, which we interpret to be S+ and H2S+, with (S+ + H2S+)/(Na+ + Mg+) = 0.67 +/- 0.06, and from water-group ions around m/q = 18, at an abundance of 0.20 +/- 0.03 relative to Na+ plus Mg+. The fluxes of Na+, O+, and heavier ions are largest near the planet, but these Mercury-derived ions fill the magnetosphere. Doubly ionized ions originating from Mercury imply that electrons with energies less than 1 kiloelectron volt are substantially energized in Mercury's magnetosphere.     

Computer graphic display method for visualizing three-dimensional biological structures

A computer graphic display method that produces two-dimensional perspective views of three-dimensional objects is presented. The method is applied to the reconstruction at a resolution of 2.2 nanometers of the neck of bacteriophage phi 29, obtained from transmission electron micrographs processed by the direct Fourier method. The combined use of directed illumination, reflectance models, color, and different levels of transparency provides a powerful tool for a better interpretation of the three-dimensional structure, allowing improved correlation with genetic, structural, and biochemical data.