عنوان مقاله [English]
Introduction: An emerging field of nanotechnology in recent years is the use of nanoparticles and nanomaterials in agricultural systems which is due to their excellent mechanical, electrical, optical, surface properties, crop protection and nano-fertilizers. Titanium dioxide (TiO2) is a class of nanoparticles which widely used in the food industry, cosmetics, papers, pharmaceuticals, plastics and industrial raw materials. The widespread industrial application of TiO2 is due to its white pigment, ultraviolet blocking property, and chemical features commonly used to alleviate pollutants concentration in water, soil and air. Owing to its increasing use in the industry, a large part of TiO2 residues are released into the environment, and currently, TiO2 nanoparticles are being considered an emerging environmental contaminant. However, there have been a number of studies reporting beneficial effects of TiO2 on growth and physiological traits of crops. It has been postulated that the TiO2-induced improvement of crop growth is not merely related to the promotion of photosynthesis; other biochemical processes especially nitrogen metabolism are also involved in this event. Ethylene diamine tetraacetic acid (EDTA) is a widely used as a chelating agent, i.e., the chemical is able to sequester metal ions such as Ca2+ and Fe3+. EDTA is used as nitrogen source for doping of TiO2 nanoparticles which improves TiO2 photocatalytic features. The present study was conducted to investigate the effects of TiO2 nanoparticles and EDTA on growth indices and biochemical parameters in spinach (Spinacia oleracea). For detailed evaluation of treatment effects, different concentrations of TiO2 nanoparticles were sprayed on spinach leaves and the samples were collected in a time course.
Materials and Methods: A factorial experiment was carried out in the form of completely randomized design (CRD) with three replications. Soil samples were taken before cultivation of spinach (S. oleracea) seeds (Var VIROFLAY) and analyzed for nutrients’ concentration. Treatments include different levels of TiO2 (T1=0, T2=0.05mg/l and T3=0.1mg/l) and two concentrations of EDTA (E1=0 and E2=130mg/l) sprayed on spinach plants in research greenhouse of agriculture faculty, Ferdowsi University of Mashhad. Aqueous solutions of nanoparticles were treated by ultrasound for 10 min to enhance homogeneity. The solutions were sprayed on the plant at six- leaves stage. The plant samples were taken before reproductive phase for measurement of biochemical parameters. Nitrogen content of plant samples was measured by PDV 500 Macro- Kjeldahl device; Potassium content was determined by 310c flame photometer; phosphorus concentration in plant samples was measured by spectrophotometer model 2100. Chlorophyll and carotenoid contents were measured by the method proposed by Lichtenthaler (1978). For analysis of growth parameters, plant samples were taken a week after TiO2 treatments and leaf area, shoot fresh/dry weight, stem length, internode length, root area, root fresh/dry weight and total root diameter were measured.
Results and Discussion: Application of 0.05mg/l of TiO2 nanoparticles without EDTA resulted in 13.5% and 9.48% increase in nitrogen and protein; respectively, however by increasing nanoparticles to 0.1mg/l, nitrogen and protein content in the treated plants were respectively reduced to 21% and 19.57% of those of control group (p