Selenium mitigates the loss of nutritional quality in rice grown at an elevated concentration of carbon dioxide

Atmospheric CO₂ enrichment has the potential to improve rice (Oryza sativa L.) yield, but it may also reduce grain nutritional quality, by reducing mineral and protein concentrations. Selenium (Se) fertilization may improve rice grain nutritional composition, but it is not known if this response extends to plants grown in elevated carbon dioxide concentration (eCO₂). We conducted experiments to identify the impacts of Se fertilization on yield and quality of rice grains in response to eCO₂. The effect of the Se treatment was not significant for the grain yield within each CO₂ condition. However, the reduction in macronutrients and micronutrients under eCO₂ was mitigated in grains of plants fertilized with Se. Fertilization with Se increased the concentration of Se in roots, flag leaves, and grains independently of atmospheric CO₂ concentrations. Elevation of the transcripts of ion transport-related genes could, at least partially, explain the positive relationship between mineral concentrations and grain mass resulting from Se fertilization under eCO₂. Treatment with Se also increased the accumulation of total protein in grains under eCO₂. Overall, our results revealed that Se fertilization represents a potential asset to maintain rice grain nutritional quality in a future with rising atmospheric CO₂ concentration.