23Na NMR microimaging: a tool for non-invasive monitoring of sodium distribution in living plants
Markus Rokitta A C , Danielle Medek A , James M. Pope B and Christa Critchley AA Department of Botany, The University of Queensland, St. Lucia, Qld 4072, Australia.
B School of Physical and Chemical Sciences, Queensland University of Technology, Gardens Point, Qld 4001, Australia.
C Corresponding author; email: rokitta@gmx.net
Functional Plant Biology 31(9) 879-887 https://doi.org/10.1071/FP04063
Submitted: 1 April 2004 Accepted: 5 July 2004 Published: 27 September 2004
Abstract
Detailed knowledge of the sodium (Na) distribution within the tissues of highly salt-tolerant Australian native species could help in understanding the physiological adaptations of salt-tolerance or salt-sensitive plants. 23Na nuclear magnetic resonance (NMR) microimaging is presented as a tool to achieve this goal. Maps of the Na distribution in stem tissue were obtained with an in-plane resolution of approximately125 µm and a slice thickness of 4 mm. Simultaneously recorded high resolution 1H NMR images showing water distribution in the same slice with 31 µm in-plane resolution and 1 mm slice thickness, were used as an anatomical reference together with optical micrographs that were taken immediately after the NMR experiments were completed. To quantify the Na concentration, reference capillaries with known NaCl concentrations were located in the NMR probe together with the plant sample. Average concentration values calculated from signal intensities in the tissue and the capillaries were compared with concentration values obtained from atomic emission photometry and optical microscopy performed on digested stem sections harvested immediately after NMR experiments. Results showed that 23Na NMR microimaging has great potential for physiological studies of salt stress at the macroscopic level, and may become a unique tool for diagnosing salt tolerance and sensitivity.
Keywords: Avicennia marina, Casuarina glauca, environmental stress, NMR microimaging, plant water relations, salinity, 23Na NMR.
Acknowledgments
The authors thank John Bertram, Lina Daddow and Lui Weber for their help with the optical microscopy, Patrick Stevens for his support with atomic emission photometry and Dr Rana Munns, Prof. Tim Flowers and Dr Roger Meder for their suggestions to improve the manuscript. This work was supported by a grant from the German Academic Exchange Service (DAAD), Gemeinsames Hochschulsonderprogramm III von Bund und Ländern and a University of Queensland Postdoctoral Research Fellowship to MR.
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