Fig. 4

Chlorophyll a fluorescence (ChlF) transients of two contrasting A. thaliana accessions, Rsch (solid line) and Co (dotted line) measured after ~20 min of dark-adaptation (DA, black lines), and after 2 h of acclimation to half of the adaptive irradiance (LI, 50 µmol photons m⁻² s⁻¹, magenta lines) or adaptive growth-irradiance (AI, 100 µmol photons m⁻² s⁻¹, blue lines). The basic parameters: minimal fluorescence (F _O), maximum fluorescence (F _M), peak under prevailing actinic irradiance (F _P), steady state fluorescence under actinic light (F _S), maximum fluorescence at steady state fluorescence (\(F_{\text{M}}^{\prime }\)), and maximum fluorescence during relaxation after switching off of actinic light (\(F_{\text{M}}^{\prime \prime }\)), are indicated in the measured ChlF of dark-adapted plants. Each curve is an average of four data sets measured from independent plants and averaged over the whole rosette area