Effect of different forms of selenium on the plant–soil–earthworm system

Abstract

AbstractSelenium (Se) is an essential micronutrient for humans, animals, and certain lower plants, but at higher concentrations Se becomes toxic to organisms. The boundary between the Se beneficial effect and its toxicity is narrow and depends on its chemical form, applied concentration, and other environmentally regulating factors. Due to the potential risk of toxicity in higher concentration, the aim of this study was to estimate the impact of increased concentrations of different forms of Se on the response of the wheat–soil–earthworm system. Soil, earthworms, and wheat grains were exposed to the Se in form of selenite and selenate in concentrations of 0.01, 0.1, and 1 mg kg−1. As an indicator of oxidative stress in wheat, lipid peroxidation levels (LPO) and total H2O2 content were determined, while antioxidative response was determined by catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR) activities. The biomarker responses in earthworms were determined by acetylcholinesterase (AChE), carboxylesterase (CES), and antioxidative enzymes (CAT and glutathione S‐transferase) activities. Selenite and selenate increased Se content in the wheat and earthworms, while selenate application was more efficient, indicating higher bioaccumulation of this Se form. Both Se forms did not cause significant changes in the LPO level and H2O2 content, while GPX activities were elevated in all treatments, suggesting that oxidative stress was not induced in wheat. In earthworms, Se significantly reduced activities of AChE and CAT at some concentrations, while CES activity was increased at all concentrations applied. This study showed significant impact of Se on measured biochemical responses in wheat and earthworms, indicating the disruption of homeostasis. Obtained results can serve as basis for further studies on Se effects and will help in including different aspects necessary for understanding of Se impact on different components of soil ecosystems.