The suspected antagonism between selenite and arsenite in various mammalian species gave reason to investigate the effect of selenite on arsenate toxicity in higher plants using Thunbergia alata as a model plant. Here, we present a study involving (1) toxicity tests, (2) uptake and translocation experiments as well as (3) selenium-sulfur-arsenic speciation analysis by HPLC-ESMS-ICP-MS (oxygen) of selected plant tissues. The EC50 (effective concentration that inhibits growth by 50%) values, as a result of the toxicity studies, showed that selenite co-exposure enhances arsenate toxicity. The detection of two selenium species, Se-II-PC2 complex and Se-cysteinylserine glutathione, suggested that the increased toxicity symptoms might have been a result of the competition of Se-II with As-III for sulfhydryl groups (crucial for arsenite detoxification in plant cells) as binding partners.
- oxidative stress