Genome size dynamics in Artemisia L. (Asteraceae): following the track of polyploidy.

Polyploidy is a key factor in the evolution of higher plants and plays an important role in the variation of plant genomes, leading to speciation in some cases. During polyploidisation, different balancing processes take place at the genomic level that can promote variation in nuclear DNA content. We estimated genome size using flow cytometry in 84 populations of 67 Artemisia species and one population of Crossostephium chinense. A total of 73 sequences of nrDNA ITS and 3'-ETS were newly generated and analysed, together with previously published sequences, to address the evolution of genome size in a phylogenetic framework. Differences in 2C values were detected among some lineages, as well as an increase of genome size heterogeneity in subgenera whose phylogenetic relationships are still unclear. We confirmed that the increase in 2C values in Artemisia polyploids was not proportional to ploidy level, but 1Cx genome size tended to decrease significantly when high ploidy levels were reached. The results lead us to hypothesise that genome size in polyploids tends to a maximum as it follows saturation behaviour, in agreement with the Michaelis-Menten model. We tested different arithmetic functions with our dataset that corroborated a non-linear relationship of genome size increase in polyploids, allowing us to suggest a theoretical upper limit for the DNA content of this genus.

Transfer of nitroglycerine to hands during contact with commercial explosives.

The techniques of thin-layer chromatography, gas chromatography with electron capture detection, and gas chromatography/mass spectrometry were used to analyze hand swab extracts for the presence of nitroglycerine. Both the amount of nitroglycerine transferred to the hands after handling commercial explosives and its persistence were measured. Gas chromatography-electron capture detection was found to be the most accurate and sensitive technique for making such determinations, especially if the extract was partially purified by thin-layer chromatography prior to analysis. The lowest limit of detection was 10 ng of nitroglycerine, and residues could be detected over 20 h after handling the raw explosive.

Assessment of solvents for the recovery of nitroglycerine from hands using cotton swabs.

Eight solvents were compared for their relative efficiency in removing nitroglycerine from the hands of persons handling explosives. The amount of interfering material also removed from the hands by the cotton swabs and the stability of the nitroglycerine in the solvent used were also investigated. Aqueous solvents yielded the best recoveries, when the extracts were partially purified by thin-layer chromatography before analysis, but the explosive was degraded rapidly by microorganisms that grew in the solutions. Of the aqueous, organic, and polar solvents tested, ethanol was found to offer the most complete, consistent, and stable recovery.