Effects of Zinc Oxide Nanoparticles (ZnO) on Improving Morpho-physiological, Yield and Its Components of Soybean (Glycine max L.) var. Williams under Salinity Stress

To evaluate the effect of zinc oxide nanoparticles (ZnO) on morphological, physiological and seed yield of soybean and its components under saline conditions, an experiment a factorial experiment base on completely randomized design with three replications was conducted at the research greenhouse of the Faculty of Agriculture, Ferdowsi University of Mashhad, Iran in 2017. The first factor consisted of four levels of salinity (0, 4, 6.5 and 9 dS.m-1), and the second factor of three concentration of zinc oxide nanoparticles (ZnO) (0, 200 and 400 ppm). The results showed that foliar spraying 200 ppm nano-ZnO resulted in higher plant height, number of leaves and dry shoot weight than other nano-ZnO levels (zero and 400 ppm) in 6.5 and 9 dS.m-1 salinity. The highest stomatal conductance (11.2 μMH2O.m-2.S-1), relative water content (83.6%) and membrane stability index (80.7%) were obtained from application 200 ppm nano-ZnO at salinity level of 4 dS.m-1. Maximum number of seeds per plant (11.4) and seed weight per plant (2.24 g) were also recorded from 200 ppm nano-ZnO under salinity of 4 dS.m-1. At all levels of salinity stress, when enhancing concentration from zero to 200 ppm the amount of all studied traits were increased and with increased concentration of nano-ZnO from 200 to 400 ppm, all experimental traits were decreased due to toxicity effect induction of nano-ZnO on plant. In general, the results showed that sprying plant with 200 ppm zinc oxide nanoparticles improved soybean growth at 6.5 and 9 dS.m-1salinity stresses