Time-resolved laboratory µ-XRF reveals silicon distribution in relation to manganese toxicity in soybean and sunflower.

Synchrotron- and laboratory-based micro-X-ray fluorescence (µ-XRF) is a powerful technique to quantify the distribution of elements in physically large intact samples, including live plants, at room temperature and atmospheric pressure. However, analysis of light elements with atomic number (Z) less than that of phosphorus is challenging due to the need for a vacuum which of course is not compatible with live plant material, or the availability of a helium environment.A new laboratory µ-XRF instrument was used to examine the effects of silicon (Si) on the manganese (Mn) status of soybean (Glycine max) and sunflower (Helianthus annuus) grown at elevated Mn in solution. The use of a helium environment allowed for highly sensitive detection of both Si and Mn to determine their distribution.The µXRF analysis revealed that when Si was added to the nutrient solution, the Si also accumulated in the base of the trichomes, being co-located with the Mn and reducing the darkening of the trichomes. Like soybean, the addition of Si did not reduce the concentrations of Mn in accumulations despite seeming to reduce its adverse effects.The ability to gain information on the dynamics of the metallome or ionome within living plants or excised hydrated tissues can offer valuable insights into their ecophysiology, and laboratory µ-XRF is likely to become available to more plant scientists for use in their research.