Each dot is the mean ± SE.

D50/N50: ½ strength Hoagland's solution (HS) during the day (D50), ½ strength HS during the night (N50); D25/N75: ¼ strength HS during the day (D25), ¾ strength HS during the night (N75); D25/N50: ¼ strength HS during the day (D25), ½ strength HS during the night (N50).

Figure 3. Net CO2 assimilation (An), stomatal conductance, and leaf transpiration in lettuce leaves for each treatment at photosynthetic photon flux (PPFD) levels between 0 and 2000 μmol m-2 s-1.