The Effect of Exogenous Selenium Supplementation on the Nutritional Value and Shelf Life of Lettuce

Abstract

Lettuce (Lactuca sativa) is rich in vitamins, minerals, and bioactive components, serving as an important source of selenium (Se) intake for humans. This study investigated the effects of Se treatment on lettuce using different concentrations of sodium selenite (Na2SeO3), focusing on biomass, physiological indicators, nutritional composition, and physiological changes during storage. Through correlation analysis of the transcriptome and Se species, the absorption and conversion mechanisms of Se in lettuce were revealed. The results showed that Se treatment initially increased the chlorophyll content in lettuce, followed by a decrease. Soluble sugar, soluble protein, total phenols, and anthocyanins increased at low Se concentrations but decreased at high concentrations. Flavonoid content decreased only at 1 mg/L Se, while other treatments were higher than the control group. GSH content and superoxide dismutase, catalase, and peroxidase activities initially increased and then decreased, while malondialdehyde (MDA) content first decreased and then increased. Five Se species, including Se (IV), Se (VI), selenocysteine (SeCys2), selenomethionine (SeMet), and methylselenocysteine (MeSeCys), were detected in lettuce leaves after Se treatment, with SeMet being the most abundant. During storage, Se-treated lettuce exhibited lower weight loss, a*, b*, browning index, and color difference (ΔE) values compared to the control group. CAT and POD activities and GSH content also followed a trend of initial increase followed by a decrease. Transcriptome data analysis revealed that genes such as MYB1, RPK1, PTR44, NTRC, WRKY7, and CSLD3 were associated with the stress response of Se-treated lettuce.