Effects of selenate and selenite on selenium accumulation and speciation in lettuce

Lettuce is a common vegetable in hydroponic production. In this paper, a selenium (Se)-biofortification method was provided. The Se content, speciation, and the effects of different concentrations of selenate and selenite on lettuce growth and amino acids were investigated. The results showed that lettuce had strong ability to accumulate exogenous selenium, and inorganic Se could be effectively converted into organic Se. The proportion of organic Se in the shoots under treatment with 4 μmol L−1 selenite was 100%. Selenomethionine was the main organic Se, accounting for 51% (selenate) and 90% (selenite) of the total Se. Adding Se improves photosynthesis of lettuce and promotes growth. The growth with 2 μmol L−1 selenate and 4 μmol L−1 selenite was better than CK, and the shoot fresh weight was increased by 143.22% and 166.98%, respectively. Furthermore, the optimum Se application is 2 μmol L−1, and some areas can apply 4 μmol L−1 selenite. But Se-excessive areas are not recommended to grow selenium-rich foods. Therefore, lettuce has strong biofortification potential. •Selenomethionine is the predominant selenium speciation in Se-biofortified.•No potential risk was found with apply low concentrations of exogenous selenium.•Selenite is safer and more effective for selenium supplementation.•Se-biofortified lettuce may be a suitable selenium supplement for increasing Se intake human.