Concentrations of phenolic compounds, percent of total N invested in chlorophylls and percent of total N attributable to PAL activity in red and green lettuce cultivated at different nitrogen concentration and photosynthetic photon flux density.

Nitrogen (N) concentration in the nutrient solution is given in millimol per liter (mM). Photosynthetic photon flux density (PPFD) is given in μmol m−2 s−1. Phenolics concentration is given in milligram per gram dry matter. Data was evaluated via two-way ANOVA, factors: mM N and PPFD, α = 0.05, followed by Tukey HSD test (mean, n = 3). Identical letters indicate that values do not differ significantly. Asterisks indicate significantly influential factors. Cy3MG = cyanidin-3-O-(6΄΄-O-malonyl)-glucoside, Q3MG = quercetin-3-O-(6΄΄-O-malonyl)-glucoside, Q3Gc/L7Gc = quercetin-3-O-glucuronide and luteolin-7-O-glucuronide.Concentrations of phenolic compounds, percent of total N invested in chlorophylls and percent of total N attributable to PAL activity in red and green lettuce cultivated at different nitrogen concentration and photosynthetic photon flux density.