Speciation plays an important role in the toxicology of elements in natural systems but due to the complexity and expense of determining chemical species in the environment it is often overlooked. Selenium (Se) is an essential micronutrient that is supplied by diet to higher animals but presents a problem with toxicity if the dietary levels are too low or too high. This is largely due to the lack alternative mechanisms of uptake, in higher animals, if the levels are too low. Conversely, there are no fast mechanisms of excretion if the levels exceed upper limits in higher animals. The regulation of Se in plants is therefore of great interest as it is a control point for dietary availability of Se. Selenium also exists in two primary forms in natural lotic systems with the common dominant form being selenate (Se(VI)) and the minor form being the more toxic selenite (Se(IV)). Previous environmental work indicated a correlation between Se species availability and the presence of Iron (Fe) in the lotic system. This study explored the dependency of Se species in Physcomytrella patens. P. patens were exposed to differing concentrations of selenium species during a static and dynamic exposures. P. patens generally had more a statistically significant stable uptake when Se(VI) and iron were present (R2=0.994, p=0.0005). There was a nearly statistically significant (95%) logarithmic trend with the uptake of Se(VI) in P. patens vs Se(VI) in media when there was no Fe present (R2= 0.828, p=0.051). When P. patens were exposed to Fe positive media and Se(IV) resulted in a Statistically significant positive correlation (R2 =0.940, p=0.006). The Fe absent and Se(IV) exposure exhibited a Statistically significant linear relationship (R2 = 0.812, p=0.037).When an analysis of variance was completed, it was determined that the slope of the Se(IV) trends are statistically different than those of Se(VI), and there was an interaction between the categorical Fe variable interaction with Se(IV) with a p-value of 0.003. These results indicate that Fe affects the uptake of Se(VI) and Se(IV) and there is an interaction between Fe and Se(IV) in P. patents. This interaction needs to be considered when using plants as biosensors for determining partitioning coefficients of Se species in contaminated streams.

Effects of iron on the bioavailability of selenium species in Physcomitrella patens

ACS Spring Meeting 2021

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