2.5 Assessment of photosystem II parameters
PSII efficiency was assessed using the Chl a fluorescence induction (FI) technique. We used the multifunctional plant efficiency analyser (M-PEA; Hansatech, King Lynn, Norfolk, UK) for the evaluation of PSII parameters as described in details by Essemine et al. (2017). Plants were dark-adapted for at least one hour at 25°C before measurements. Then, healthy and fully expanded leaves were exposed to saturating orange-red (625 nm) actinic light (5,000 µmol m-2 s-1) provided by the LED for 1 second. The ratio of variable fluorescence level Fv(Fm-F0) to maximal fluorescence level Fm (Fv/Fm) was used to evaluate the maximum efficiency of PSII. Fm (P-level) represents the maximum yield of Chl a fluorescence and F0 (O-level) is the minimum Chl a fluorescence (the intensity of Chl a fluorescence of dark-adapted sample with a measuring beam of negligible actinic light intensity). Fv/F0 parameter represents the functional reaction center of PSII. All the parameters listed in the Table S1 were calculated from the original OJIP curves according to the so-called JIP-test (Strasser et al., 2004)