Photosynthetica X:X | DOI: 10.32615/ps.2026.031

Validation of the newly developed PlantECG fluorometer against three established chlorophyll fluorescence devices under progressive drought stress in pepper, tomato, and strawberry plants

H.M. KALAJI1, 2, P. DˇBROWSKI3, A. AURIGA4
1 Warsaw University of Life Sciences, Department of Botany and Plant Physiology, Nowoursynowska 159, 02-776 Warsaw, Poland
2 Zielona Fundacja, ul. Wiatraki 3E, 21-400 Łuków, Poland
3 Warsaw University of Life Sciences, Department of Environmental Development and Remote Sensing, Nowourysnowska 159, 02-776 Warsaw, Poland
4 West Pomeranian University of Technology in Szczecin, Faculty of Biotechnology and Animal Sciences, al. Piastów 17, 70-310 Szczecin, Poland

Comparing chlorophyll fluorescence data across different fluorometers remains challenging. We compared the new PlantECG fluorometer with PocketPEA, HandyPEA, and FluorPen in pepper (Capsicum annuum L.), tomato (Solanum lycopersicum L.), and strawberry (Fragaria × ananassa Duch.) under progressive drought (0-96 h without irrigation). The maximum quantum yield of PSII photochemistry (FV/FM) measured by PlantECG correlated strongly with all reference devices (R2 = 0.72-0.98), although PlantECG slightly overestimated FV/FM under severe stress. The performance index (PIABS) showed greater inter-device divergence, with strong correlations in pepper and strawberry (R2 = 0.81-0.89) but weaker ones in tomato (R2 = 0.59-0.67). Absolute PIABS values differed substantially: PlantECG values were closest to PocketPEA, whereas HandyPEA recorded 2-5-fold lower values. Correlation quality depended on the species-specific rate of drought response. PlantECG reliably tracks drought-induced changes in photosynthetic performance, but species-specific calibration is required before comparing its absolute PIABS values across instruments.

Additional key words: chlorophyll fluorescence; drought stress; fluorometer comparison; FluorPen; HandyPEA; photosystem II; PlantECG; PocketPEA.

Received: May 13, 2026; Revised: July 27, 2026; Accepted: September 16, 2026; Prepublished online: October 7, 2026 

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