Investigating the application of ZnO nanoparticle on morphological and physiological parameters of two cultivars of Fenugreek (Trigonella foenum-graecum L.) under salinity stress

Salinity stress is one of the environmental factors limiting plant growth and development and has negative effects on morphological and physiological parameters of plants. Therefore, various compounds have been used to reduce the harmful effects of this stress. According to previous studies, metal nanoparticles have both negative and positive effects on different plant species. The aim of this study was to investigate interaction effects of different concentrations of ZnO nanoparticle and NaCl on morphological parameters, photosynthetic pigments and protein content in Ardestanian and mashhadian cultivar of Fenugreek. Factorial experiment was performed in a completely randomized design with three replications and three levels of ZnO nanoparticle (0, 1000 and 3000 ppm) and four levels of NaCl (0, 75, 150 and 225 mM) were used. The results showed that salinity stress significantly decreased shoot and root fresh weight, as well as the percentage of relative water content root at 225 mM NaCl in both cultivars. The highest fresh weight of shoot in Mashhadian cultivar was observed in the interaction of 75 mM NaCl and 1000 ppm of ZnO nanoparticle. In general, ZnO nanoparticles improved fresh and dry weight in both cultivars. In Ardestanian cultivar, the highest amount of phenol was observed in the concentration of 3000 ppm of nanoparticle and 225 mM NaCl, also the highest flavonoid content was observed in the interaction of 3000 ppm of nanoparticle and 150 mM NaCl. The highest photosynthetic pigments were observed at interaction of 75 mM NaCl and 3000 ppm of nanoparticle in two cultivars. Increasing the concentration of nanoparticle also led to a significant increase in carotenoids in both cultivars. The most antioxidant activity based on IC50 was in Mashhadian cultivar and in the interaction of 225 mM NaCl and 3000 ppm of nanoparticle. The results of this study showed that the application of ZnO nanoparticle under salt stress caused the growth of the plant to improve.