Peer review

With rising air pollution and global warming, the threat of impending drought in agricultural areas is a frightful scenario. Mitigation of such types of drought stress in Indian context is all the more important as Climate Change induced drought is poised to affect Indian farms in the future. The alleviation of abiotic stress in plants by employing iron oxide nanoparticles (FeNp) is a novel approach, not much reported. Hence, in the present study we undertook green synthesis of Iron oxide nanoparticles/magnetite (Fe3O4-Np) from a marine algae Chaetomorpha antennina (green algae). Henceforth, two types of Iron oxide nanoparticles were synthesized, characterized and employed further – bare FeNp and citrate coated FeNp. The biogenic iron oxide nanoparticles have been employed as a nano-fertilizer. However its active mechanism in the amelioration of drought stress is unknown. Henceforth, we wanted to establish the role of FeNp under drought stressed conditions and by coating it further with citrate we observed an enhanced stress amelioration effect. Drought stressed Setaria italica plants were treated with green synthesised iron oxide nanoparticles, both bare as well as capped. These FeNp not only serve as a nanonutrient for the plant, but also enabled the plant to overcome drought stress. An overall increase in the plant (Setaria italica) growth was detected. It was also observed that with increasing concentrations of FeNp (Fe3O4), the seedlings showed a concomitant increase in chlorophyll as well as soluble sugar content, suggesting that the iron up taken by the plants were used up for producing photoassimilates. The iron, H2O2 as well as proline content in the plants was also estimated, which further confirmed that the plants readily uptook FeNp and overcame the drought stress. Thus we could conclude from our experiments that, FeNp (both capped as well as bare FeNp) are effective in conferring the plants, ability to ameliorate drought stress. Throughout the experiment no toxic effect was observed in the plants. This confirms the potential of green synthesized FeNp, as an eco-friendly fertilizer even under drought stressed conditions.

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