# Carbon dioxide-enriched atmosphere diminished the phytotoxicity of neodymium in wheat (Triticum aestivum L.)

## TL;DR

Elevated CO2 levels reduce the harmful effects of neodymium on wheat growth and photosynthesis.

## Contribution

This study shows that elevated CO2 mitigates neodymium-induced phytotoxicity in wheat.

## Key findings

- Elevated CO2 reduced neodymium accumulation in wheat tissues.
- Elevated CO2 improved photosynthesis and antioxidant defenses in neodymium-treated wheat.
- Elevated CO2 enhanced Rubisco activity and PSII efficiency in wheat under neodymium stress.

## Abstract

Neodymium (Nd), a rare earth element (REEs), is widely utilized in industry. Although the detailed biological role of Nd in plant biology is unclear, recent reports have noted its oxidative phytotoxicity at concentrations higher than 200 mg kg-1 soil. At present it is unclear if these detrimental effects could be offset by the global rise in atmospheric carbon dioxide concentration ([CO2]) which has been shown to enhance photosynthesis and growth in a wide range of C3 plant species.

To assess any amelioration effects of [CO2], a phytotoxic dose of Nd (III) was given to wheat grown under two scenarios of atmospheric CO2, ambient levels of CO2 (aCO2, 420 ppm) and eCO2 (620 ppm) to assess growth and photosynthesis.

Our results suggest that at ambient [CO2], Nd treatment retarded wheat growth, photosynthesis and induced severe oxidative stress. In contrast, eCO2 reduced the accumulation of Nd in wheat tissues and mitigated its negative impact on biomass production and photosynthesis related parameters, i.e., photosynthetic rate, chlorophyll content, Rubisco activity and photochemical efficiency of PSII (Fv/Fm). Elevated [CO2] also supported the antioxidant defense system in Nd-treated wheat, enhanced production of enzymatic antioxidants, and more efficient ascorbate-glutathione recycling was noted. While additional data are needed, these initial results suggest that rising [CO2] could reduce Nd-induced oxidative stress in wheat.