The results of series of experi-
ments, performed with 638 nm LED light (supplemental for natural and HPS illumination) pre-harvest treatment
in greenhouses present the increased antioxidant capacity, enhanced contents of phenolic compounds and alpha
tocopherol (Žukauskas et al. 2011, Samuolienė et al. 2012a) as well as reduced nitrate contents (Samuolienė et
al. 2009, Samuolienė et al. 2011) in different lettuce varieties and other leafy vegetables (Bliznikas et al. 2012