Figure 3.

The quantum yield of photosystem II (Φ_PSII = 0.792 − 0.000663 × PPFD) (A) and the electron transport rate [ETR = −10.1 + 112.1 × (1 − e^{−0.00463 × PPFD})] (B) of lettuce (Lactuca sativa ‘Green Towers’), averaged over the entire photoperiod, as a function of photosynthetic photon flux density (PPFD) Data points represent the mean ± SD (n = 3). Plants were measured under two daily light integrals (DLI), 15 and 20 mol m⁻² d⁻¹, but DLI had no effect on the relationship between PPFD and these parameters.