Photosynthetica X:X | DOI: 10.32615/ps.2026.035

Quantification of spatial heterogeneity of different chlorophyll fluorescence parameters over tomato leaf areas affected by Cd2+ stress

D. GIORDANO1, †, A. SAADATI2, †, A.M. ASHRAFI3, L. RICHTERA4, M. BARTÁK1
1 Laboratory of Photosynthetic Processes, Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 5, 625 00 Brno, Czech Republic
2 Central European Institute of Technology, Brno University of Technology, Purkyňova 123, 612 00 Brno, Czech Republic
3 Institute of Photonics and Electronics of the Czech Academy of Sciences, Chaberská 57, 182 00 Prague 8, Czech Republic
4 Department of Chemistry and Biochemistry, Mendel University in Brno, Zemědělská 1665/1, 613 00 Brno, Czech Republic

Cadmium impairs plant growth by inducing oxidative damage through excessive ROS production. Sulfur and nitrogen supplementation can affect Cd mobility, uptake, and toxicity. This study quantifies the spatial heterogeneity of Cd-induced photochemical limitation in Solanum lycopersicum leaves using chlorophyll fluorescence imaging, and examines Cd2+ distribution in roots, stems, and leaves of hydroponic plants treated with ammonium sulfate. We assessed four treatments: control, ammonium sulfate (5 mM), cadmium (100 µM CdCl2), and their combination, using fluorescence imaging, the JIP-test, and polarography. Cd stress was intrinsically heterogeneous within single leaves, with the strongest PSII inhibition along vascular tissue and leaf tips. Contrary to expectations, ammonium sulfate failed to mitigate Cd toxicity, suggesting an adverse ammonium-Cd interaction. OJIP analysis revealed severe oxygen-evolving complex damage under combined treatment, marked by prominent K- and L-bands. These findings highlight the localised nature of Cd stress and reveal responses missed by whole-leaf measurements.

Additional key words: cadmium ion stress; chlorophyll fluorescence; OJIP; Solanum lycopersicum; spatial heterogeneity.

Received: June 25, 2026; Revised: August 22, 2026; Accepted: September 23, 2026; Prepublished online: October 15, 2026 

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