The same parameters were also measured in light-adapted leaves, with F′0 being the minimum fluorescence, F′M the maximum fluorescence and the operational photochemical efficiency.
The ratio of variable fluorescence to maximum fluorescence (Fv/Fm), representing the maximum photochemical efficiency of photosystem II (PSII), was determined using a portable chlorophyll fluorometer (OptiSci OS-30p Chlorophyll Fluorometer, Opti-Sciences Inc, USA).
The ratio of variable to maximum fluorescence (Fv/ Fm) was used as an indicator of the maximum quantum efficiency of photosystem II.
QY represents the ratio of variable fluorescence (Fv = Fm − F0) to maximum fluorescence (Fm), with QY = Fv Fm used as a proxy of photochemical quenching efficiency [70].
The maximal quantum efficiency (Fv/Fm) of PSII was determined as the ratio of variable fluorescence (Fv) to maximum fluorescence of dark-adapted state (Fm).
The minimum (F0) and maximum fluorescence (Fm) was measured at the end of a dark-acclimation period (3 min) and the maximum quantum yield (the PSII efficiency) was calculated from Fv/Fm, where Fv is the variable part of fluorescence emission and equal to Fm F0.
The maximum quantum efficiency of PSII (Fv/Fm) was calculated from (Fm-Fo)/Fm, where Fo, Fm, and Fv are ground fluorescence, maximum fluorescence of the dark-adapted subjects, and maximum variable fluorescence, respectively [ 41].
maximum fluorescence intensity.
Chlorophyll fluorescence measurements included initial fluorescence (Fo), maximum fluorescence (Fm) and variable fluorescence (Fv).
the maximum fluorescence at the steady state.
