Fig. 8
Chlorophyll fluorescence measured at a PPFD of 300 μmol m-2 s-1 at room temperature in the three tomato cultivars under four days of control, drought, heat and combined stress. Different sub-graphs represent a Fv/Fm on dark-adapted leaves, b quantum efficiency of PSII (ΦPSII), c electron transport rate (ETR), d fraction of open PSII centers (qL) and e non-photochemical quenching (NPQ). The data represent mean values ± SE (n = 4). Different small letters above the bars indicate significant differences (P < 0.05)