Elicitation with hydrogen peroxide promotes growth, phenolic-enrichment, antioxidant activity and nutritional values of two hydroponic lettuce genotypes

Dietary vegetables rich in bioactive compounds are major responsible for promoting human health. Herein, the effect of hydrogen peroxide (H(2)O(2)), an important signaling compound, on growth and quality of two hydroponic lettuce genotypes was investigated. The maximum enhancement of growth traits was shown in lettuce elicited with 10 mmol/L H(2)O(2), while 40 mmol/L H(2)O(2) significantly reduced above growth traits. H(2)O(2) elicitation increased pigment contents and photosynthetic process, which consequently caused enhancements of phenolic compounds, ascorbic acid, glutathione, carotenoids, soluble sugars, free amino acids, soluble protein, minerals, and antioxidant capacity, while above alterations appeared in a genotype-dependent manner. The phenolic accumulation was correlated with improved activity of phenylalanine ammonia lyase (PAL) and expression levels of genes related to phenolic biosynthesis, including PAL, chalcone synthase, flavanone 3-hydroxylase, dihydroflavonol-4 reductase, and UDP-glucose: flavonoid 3-O-glucosyltransferase. Therefore, elicitation with H(2)O(2) is a promising strategy to develop lettuce with high bioactive compounds and biomass.