Interactive Effects of Selenium and Arsenic on their Accumulation, Translocation, Arsenic and Selenium Species, and Subcellular Distribution in Brassica Vegetables

Currently, co-contamination of arsenic (As) and selenium (Se) is increasingly observed in specific locales, attributable to the expansion of Se-enriched agriculture. This paper aims to elucidate the possible mechanism of As and Se interaction. In this investigation, a soil pot experiment was conducted to explore the individual and combined effects of As (arsenate, 100 mg·kg − 1 soil) and Se (selenite, 7.5 mg·kg − 1 soil) on their accumulation, translocation, speciation composition, and subcellular distribution in three Brassica vegetables. The results showed that As stress remarkably inhibited plant growth. Under As stress, the addition of Se did not significantly affect As transport factors, yet it notably increased total As content in the stems, leaves, and flowers. Se addition was observed to obstruct As conversion from inorganic to organic forms, thereby elevating both As(III) and As(V) levels in the aerial organs. Subcellular analysis revealed an increase in As levels within the leaf cell walls, organelles, and soluble cytosol. Interestingly, the impact of As on Se accumulation was found to be stimulatory in choy sum but inhibitory in pak choi and mustard. Under Se stress, As supplementation impeded the conversion of Se from inorganic to organic forms, leading to higher Se(VI) concentrations. At the subcellular level, As addition promoted Se translocation from the leaf cell wall and organelles to cytosolic, where both As and Se predominantly accumulated. These results suggest that the interaction between As and Se inhibits their metabolic processes and enhances vacuolar compartmentalization, thereby influencing their accumulation in plants. The research highlights the heightened risk of As contamination in Se-enriched vegetables cultivated in As-contaminated soil.