Nitrogen is an essential plant nutrient that promotes growth and agricultural yield. However, plants, unlike some bacteria, are incapable of nitrogen fixation, the ability to convert nitrogen from the atmosphere into a biologically useful form. Therefore, synthetic nitrogen fertilizers, which are associated with environmental pollution, are often used. In our experiments, a maize seedling was inoculated with the nitrogen-fixing bacteria Gluconacetobacter diazotrophicus in an environment enriched in
15N. The NanoSIMS hue saturation intensity images depict significant
15N enrichment above the natural abundance ratio in the chloroplasts of the resulting maize leaf, providing direct evidence that these bacteria successfully provided fixed nitrogen to the plant.
Recorded on a CAMECA NanoSIMS 50L at National Physical Laboratory, Teddington, UK. Image courtesy of Gina Greenidge.