Elucidating the phytotoxicity thresholds of various biosynthesized nanoparticles on physical and biochemical attributes of cotton

Abstract

Abstract Background A pot experiment was conducted to evaluate the phytotoxic thresholds of zinc oxide (ZnO NPs), iron oxide (FeO NPs), copper (Cu NPs), and silver nanoparticles (Ag NPs) on cotton. All the nanoparticles were biosynthesized from Conocarpus erectus L. leaf extract. They were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier transmission infrared spectroscopy (FTIR). Five concentrations (0, 25, 50, 75, and 100 ppm) of all the biosynthesized nanoparticles were foliar applied thrice over the duration of cotton growth. Five cotton seeds were sown in 5 kg soil pot and harvested after 6 weeks. SPAD values were evaluated before harvesting while physical growth parameters, physiological parameters biochemical, and oxidative stress parameters were measured after harvesting. Results The value of all parameters, except oxidative stress, increased by 13–47% in response to ZnO NPs application up to 100 ppm. However, phytotoxic threshold of iron oxide nanoparticles (FeO NPs) and copper nanoparticles (Cu NPs) was only 50 ppm as plant growth was increased by 7.9–24.3%. Above 50 ppm plant growth and biomass were decreased by 6.7–16.2%. Silver nanoparticles (Ag NPs) showed maximum growth (3.7 to 9.12% increased) at 25 ppm concentration. At higher concentrations than 25 ppm, the application of Ag NPs decreased the growth due to toxicity. Foliar application of different biosynthesized nanoparticles showed the different range of threshold value for cotton crop. Threshold value of iron oxide and copper nanoparticles for cotton was 50 ppm, whereas, it was 25 ppm for silver nanoparticles. Since the ZnO NPs application continued increasing the growth till its maximum concentration used i.e., 100 ppm, we cannot say that this is its threshold value. Conclusion On the basis of obtained results, it can be concluded that nanoparticles should be used within threshold to avoid adverse effects on crops. Application of nanoparticles within threshold optimum concentration, increased plant biomass and antioxidant system. Graphical Abstract