Stimulating effects of pre-sowing seed treatment with metal nanoparticles on winter wheat growth and development

The use of nanotechnologies in agriculture is an advanced course enabling to reduce the dependence of crop tonnage and quality on external factors. A special section is represented by studies of pre-sowing treatment of seeds with metal nanoparticles (NPs). In this work, it is shown for the first time that pre-sowing treatment of seeds with metal nanoparticles with specific physicochemical parameters affects morphometric indices of the of winter wheat growth at all stages of its development as well as the plant resistance to pathogens, grain quality, the degree of its damage from fusarium and elemental composition of the soil after harvesting. Effects depend on the type of metal used. Our aims were to study i) effects of pre-sowing seed treatment with iron, zinc, and copper NPs on the growth parameters and grain quality of winter wheat, and ii) whether this treatment affects the soil after harvest. Iron, zinc, and copper NPs were obtained by the method of high temperature condensation at the Migen-3 apparatus (Institute of Energy Problems of Chemical Physics RAS, Russia). The shape and size of NPs were evaluated by JSM-7401F scanning electron microscope (JEOL Ltd., Japan). X-ray phase analysis was carried out using an ADP-1 X-ray analyzer (NPO Modern Technologies of Non-Destructive Control, Russia). Field trials were carried out at the validation test site of the Novokuban Branch of the Rosinformagrotech (Krasnodar Territory). The predominant soil type is typical chernozem, with medium humus content, heavy loamy. The sowing of winter wheat ( Triticum aestivum L.) cv. Stan was performed on October 4, 2016 with a setting seed rate 240 kg/h. The assigned treatments were as follows: control (seeds without treatment), seed treatment with Fe NPs (5×10-4 %), Zn NPs (1×10-4 %), Cu NPs (5×10-7 %); Fe NPs + Zn NPs + Cu NPs (5×10-4 % + 1×10-4 % + 5½10-7 %). Soil samples were collected for chemical analysis. For phenological and biometric observations, plants were taken from three locations of 1 m2 area from each experimental and control plot. Plant height, average root length, thickness of the main stem at the plant bottom, tillering and depth of the tillering node were measured. Iron, zinc, and copper NPs were round single-crystal structures covered with a semitransparent oxide film. Average diameter of Fe NPs was 27.0±0.51 nm, Zn NPs 54.0±2.8 nm, Cu NPs 79.0±1.24 nm. X-ray phase analysis showed that iron NPs consisted of 53.6 % crystalline metal phase, Fe3O4 content was 46.4 %, and the oxide film thickness was 3.5 nm. Cu and Zn NPs contained only crystalline metal phases with the similar oxide film thickness, 0.5 to 1.0 nm. Pre-sowing treatment of seeds with Fe NPs affected the height of seedlings, promoted the formation of a developed root system with total root length being 4.5 % more (р ≤ 0.05) than in the control group, and increased the seedling stand density by 9.96 % (р ≤ 0.05) vs. control. Pre-harvest monitoring of crops revealed an increase in the yield of wheat plant mass after pre-sowing seed treatment with Fe and Cu NPs. Stem length was larger than that of the control (81.3±1.2 sm) by 3.8 and 8 cm, respectively, the average thickness of the main stem at the plant bottom being larger by 6 mm (when processing with Fe NPs) and 5 mm (when treating with Cu NPs) in comparison with the control (44 mm). Plant stands productivity enhancement after Fe and Zn NPs treatments, higher resistance to pathogens (by 3.85 times vs. control) under Fe NPs, a tendency to an increase in the average 1000-grain weight when using NPs of Fe, Zn, and Cu were observed. The crop quality parameters had higher values as compared to the control: in terms of the content of wet gluten by 6.12 % when seeds were treated with Zn and Cu NPs or with NPs composition; the protein mass fraction was larger under treatment with Cu NPs and the NPs composition by 5.1 % vs. control. Pre-sowing treatment with Fe and Zn NPs reduced the prevalence of Fusarium infection in grain by 1.24 and 2.25 times respectively vs. control. Elemental analysis of the soil after harvesting showed a decrease in the content of mobile forms of phosphorus by 27 % and zinc by 48 % after seed treatment with Zn NPs in comparison with the control, and a decrease in the phosphorus mobile forms by 23 % and sulfur by 7 % after pre-sowing treatment with Cu NPs in comparison with the control. The data obtained demonstrate the effective influence of the pre-sowing treatment of seeds by metal NPs on the growth, development and grain quality of wheat.