Physiological and biochemical responses of wheat to synergistic effects of selenium nanoparticles and elevated CO₂ conditions

Elevating CO2 (eCO(2)) levels will change behavior and the effect of soil fertilizers and nutrients. Selenium NPs (SeNPs) have arisen as an alternative to conventional Se fertilizers to enrich crops. However, it remains unclear whether eCO(2) will change the biological effects of soil SeNPs on plant growth and metabolism. The current study aimed to shed new light on the interactive impacts of eCO(2) and SeNPs on wheat plants. Accordingly, the attempts were to reveal whether the application of SeNPs can modulate the eCO(2) effects on wheat (Triticum aestivum L.) physiological and biochemical traits. With this goal, a pot experiment was carried out where the seeds were primed with SeNPs and plants were grown under two levels of CO2 concentrations (ambient CO2 (aCO(2), 410 mu mol CO2 mol(-1); and eCO(2) (710 mu mol CO2 mol(-1))) during six weeks after sowing. Although SeNPs+eCO(2) treatment resulted in the highest accumulation of photosynthetic pigment content in leaves (+49-118% higher than control), strong evidence of the positive impacts on Rubisco activity (similar to+23%), and stomatal conductance (similar to+37%) was observed only under eCO(2), which resulted in an improvement in photosynthesis capacity (+42%). When photosynthesis parameters were stimulated with eCO(2), a significant improvement in dry matter production was detected, in particular under SeNPs+eCO(2) which was 1.8 times higher than control under aCO(2). The highest content of antioxidant enzymes, molecules, and metabolites was also recorded in SeNPs+eCO(2), which might be associated with the nearly 50% increase in sodium content in shoots at the same treatment. Taken together, this is the first research documenting the effective synergistic impacts of eCO(2) and SeNPs on the mentioned metabolites, antioxidants, and some photosynthetic parameters, an advantageous consequence that was not recorded in the individual application of these treatments, at least not as broadly as with the combined treatment.