Concentrations of essential heavy metals, like all environmental factors, have to
be kept within an optimal range to avoid plant stress. Low concentrations may induce
deficiency, whereas toxicity arise at high concentrations. Non-essential metals might
be toxic as well. The control over their distribution in plant tissues is vital to
avoid both deficiency of essential elements, and accumulation induced toxicity. Thus,
understanding lateral distribution, compartmentalization, that support the understanding
of the underlying transport processes has a prime importance. X-ray fluorescence (XRF)
imaging is a powerful non-destructive technique that provides high-resolution elemental
maps of flat surfaces such as leaves, enabling the visualization of Fe distribution
at organ, and tissues levels. In the current study we applied a Horiba XGT-7200 desktop
imaging system for the study of organ-level distributions of essential macro- and
microelements. The system enables to reach resolutions down to 2 μm pixel width, depending
on the resolution and area settings (Gracheva et al. 2022). However, signal intensity
obtained from the K emission of essential and trace elements generally does not support
the imaging of their distribution. Indeed, obtained X-ray fluorescence still bear
valuable information. Accurate data handling is critical for precise interpretation,
and strategies for minimizing artifacts, optimizing signal-to-noise ratios, and employing
advanced image analysis methods must be used to generate qualitative and semi-quantitative
distribution profiles. XRF-based techniques are versatile and can be used to study
diverse plant species, providing a comprehensive understanding of Fe metabolism throughout
the plant kingdom. We have tested multiple plant models, including Arabidopsis thaliana,
Triticum aestivum, and Ginkgo biloba to how essential and non-essential metals can
be detected. Using elemental profiling by comparing the natural distribution of essential
and trace elements, we can identify potential interactions and co-localization patterns
for a deeper understanding of plant physiology. We highlight the key role of XRF imaging
and careful data handling in advancing knowledge of essential and trace metals in
plants. This knowledge could be used to address of tolerance to environmental stresses.
Reference
Gracheva et al. (2022). Photochem. Photobiol. Sci. 21: 983.
This work was supported by the grant K-146865 of NKFIH, Hungary. Á.S. was supported
by the János Bolyai Scholarship of the Hungarian Academy of Sciences (BO-00113-23-8).
XRF imaging facility was granted by the European Structural and Investment Funds (VEKOP-2.3.3-15-2016-00008).
