Concentrations of carotenoids 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. Concentrations are 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.Concentrations of carotenoids in red and green lettuce cultivated at different nitrogen concentration and photosynthetic photon flux density.