Abstract
Nano-sized arsenic oxide nanoparticles (As2O3-NP) limit crop growth and productivity. As2O3-NP represent a strong environmental hazard. The predicted rise in future atmospheric CO2 could boost plant growth both under optimal and heavy metal stress conditions. So far, the phytotoxicity of As2O3-NP and their interaction with eCO2 were not investigated at physiological and metabolic levels in crop species groups such as C3 and C4. We investigated how eCO2 level (620 ppm) alleviated soil As2O3-NP toxicity induced growth and mitigated oxidative damages through analysing photosynthetic parameters, primary (sugars and amino acids) and secondary (phenolics, flavonoids and anthocyanins) metabolism in C3 (barley) and C4 (maize) plants. Compared to maize, barley accumulated higher As2O3-NP level, which inhibited growth and induced oxidative damage particularly in barley (increased H2O2 and lipid peroxidation). Interestingly, eCO2 differently mitigated As2O3-NP toxicity on photosynthesis, which consequently improved sugar metabolism. Moreover, high carbon availability in eCO2 treated plants directed to produce osmo-protectant (soluble sugars and proline) and antioxidants (anthocyanins and tocopherols). In the line with increased proline and anthocyanins, their metabolism was also improved. Notable differences occurred between the two plant species. The ornithine pathway was preferred in maize while in barley proline accumulation was mainly through glutamate pathway. Moreover, under As2O3-NP stress, barley preferentially accumulated anthocyanins while maize accumulated total phenolics and flavonoids. This work contributes to improving our understanding of the differences in growth, physiological and biochemical responses of major crops of two functional photosynthetic groups (C3 and C4 plants) under ambient and elevated CO2 grown under As2O3-NP stress.
•Arsenic oxide nanoparticles (As2O3-NP) impose oxidative stress in barley and maize.•Barley and maize responded differently to As2O3-NP toxicity.•Sugars, anthocyanin and proline metabolism were remarkably different in barley and maize in response to As2O3-NP.•Elevated CO2 alleviated the As2O3-NP Toxicity.•Elevated CO2 differently affected sugars, anthocyanins and proline metabolism in barley and maize.