Shoot apical meristems as a target for gene transfer by microballistics

Summary The classical approach of gene transfer to a given plant species delivers the foreign gene to transformable cells and then puts the effort into generating plants. This approach is very difficult in many important crop plants, including cereals, and the results of regeneration are very genotype-dependent. In contrast, we use regenerable cells and try to transform them. Shoot apical meristems provide a tissue which regenerates in situ a fertile plant for most given genotypes or species. Transformation of meristem cells may lead to transgenic sectors in chimeras. These sectors may contribute to the gametes and, thus, to transgenic offspring, which then should be homohistonts and not sectorial chimeras like their parents. Our model plant for these studies is wheat. Microtargeting is a ballistic approach which is particularly suitable for the controlled delivery of microprojectiles to meristem cells in situ (Sautter et al., 1991). We summarize in this paper our experience with ballistic microtargeting of transgenes to wheat shoot apical meristem cells in situ.Abbreviations GUS -glucuronidase     

Pesticide residues in the total diet in Canada II—1970

Composites of food representing the Canadian diet were analysed for organochlorine and organophosphorus pesticides and arsenic. Thirteen organochlorine and three organophosphorus pesticides were found. Residues were consistently low and would contribute to the diet approximately 20 μg total pesticide residues and 30 μg arsenic per person per day.     

Quantification of Bacterial Populations Indigenous to Acidic Drainage Streams

Acid mine drainage (AMD) from mining activities can cause majorenvironmental problems. The acidity is due in part to the microbial oxidation of sulfide minerals in the exposed ores. Aslittle is known about seasonal variations of microbial populationsizes in AMD, the objective of this investigation was to quantifythe principal bacterial populations (iron-oxidizing acidophiles, sulfur-oxidizing acidophiles, sulfur-oxidizing neutrophiles, andacidophilic heterotrophs), with respect to season. The AMD sites sampled were four streams emerging from a copper/nickel tailingsarea. All bacterial populations with the exception of acidophilicsulfur oxidizers were recovered throughout the year. The most numerous bacteria were acidophilic heterotrophs and iron-oxidizing acidophiles. Surprisingly, there were no obvious trendsin the relative abundance of the various bacterial groups as a function of season. Recovery of the various bacterial groups at an incubation temperature of 4 °C indicated that psychrotrophic members do exist. During the course of the investigation, it was observed that thenumber of Acidithiobacillus ferrooxidans (Thiobacillusferrooxidans) colonies recovered on iron salts purified agarose,a preferred medium, was highly variable. The variability was attributed to the presence of non-iron-oxidizing satellite bacteria, the growth of which could be suppressed by increasingthe concentration of the electron donor ferrous sulfate.