Citric acid and hydrogen sulfide application reduce silver nanoparticles damage in green bean (Phaseolus vulgaris) plants

Silver nanoparticles are being extensively used in a broad range of applications in our daily routine life. In the present study, it was investigated if citric acid (CA) and hydrogen sulfide (H2S) can mitigate adverse effects of silver nanoparticles (AgNPs) in green bean plants. Green bean seedlings were applied with AgNPs either through soil drenching or foliar spray and were then treated with different concentrations of citric acid and NaHS, as H2S donor. Results indicated that AgNPs induced several stresses in green bean plants. Concomitant foliar and soil appliaction of nanoparticles caused adverse effects on photosynthetic pigments and reduced carotenoid and protein contents, while increasing H2O2 content and superoxide dismutase (SOD), and ascorbate peroxidase (APX) activities. It was revealed that citric acid and H2S application significantly alleviated adverse effects of AgNPs. In the plants challenged with AgNPs, the highest rates of catalase (CAT), glutathione S-transferase (GSTs), and malondialdehyde (MDA) activities were recorded, while these parameters were reduced when plants were also treated with H2S. Application of 1.5 g/L of citric acid caused sharp decreases in CAT, GST and MDA activities. Among the treatments, the highest levels of APX, SOD, and anthocyanin were observed in the plants treated with AgNPs trough both foliar and soil drench method without citric acid and H2S treatment. The findings of the present study would increase our knowledge of the interaction of plants with heavy metals and would be useful for designing sophisticated methods for reducing the damages in the stressed plants.