Abstract:
Graphene is a new type of carbon nanomaterial with a broad application prospect in modern agriculture in recent years. Most studies have reported that the effect of graphene on the plant growth is closely related to the amount of added graphene. An appropriate concentration can promote the growth of plants, especially the growth of plant roots, and ultimately increase the biomass of plants. However, the high amount of graphene can inhibit the growth of plants. Therefore, it is very necessary to clarify the influence of graphene on the growth and quality of various crops with the great economic value of roots, in order to explore the application potential and value. Taking the radish (a popular fleshy root vegetable crop) as the research object, this study aims to reveal the influence of graphene soaking and treatment on the growth and quality of some root-utilizing crops. A scientific basis was also provided for the graphene application in the high-efficiency and high-quality cultivation of radish. Four concentrations of graphene (0, 20, 40, and 100 mg/L) were used to treat the radish seeds and irrigate soil. An analysis was then made on the effects on the radish seed germination and field planting. In the seed germination experiment, the germination rate of radish seeds was counted to measure the bacon length, in order to characterize the effect of graphene on the radish seed germination. In the field planting experiment, the effect of graphene on the radish growth was evaluated to measure the plant height, leaf number, leaf fresh weight, and leaf length. Some photosynthetic parameters were measured to calculate the leaf Water Use Efficiency (WUE), leaf nitrogen content, fleshy root yield and weight, soluble sugar and vitamin A content, further to comprehensively evaluate the effect of graphene on the radish yield and quality. The results showed that the concentration of graphene in the range of 20-100 mg/L was greatly promoted the germination of radish seeds, where the 40 mg/L graphene presented the most significant effect. Furthermore, the growth of radish plants was significantly improved, when the concentrations of graphene were 20 and 40 mg/L in the field experiment. There was an increase in the chlorophyll content, enhanced photosynthesis, and the leaf WUE. Among them, the WUE referred to the light and function that produced by the unit transpiration water consumption of leaves. The higher WUE value indicated the stronger drought resistance of plants. Specifically, there was the higher WUE of radish leaves that treated with 20 and 40 mg/L graphene, whereas the lower with the 100 mg/L graphene, compared with the control. All graphene treatments were promoted the absorption of N by plants in the main growth and development stage of radish. A leading role of N component was found in the plant life activities, crop yield, and quality, particularly in many important organic compounds, such as the enzymes and protein, nucleic acids, vitamins, alkaloids, and plant hormones. Therefore, the graphene was applied to increase the yield of radish fleshy roots by 3.6%-13.8%. There was also an increase in the contents of soluble sugar and vitamin A. The soluble sugar was the direct product of plant photosynthesis for the normal physiological activities and functions of cells in the plant carbon metabolism. The main process was dominated by the plant growth and development, yield and quality. Vitamin A was also closely related to the plant growth and cell division. Consequently, the graphene with the appropriate concentration can be expected to promote the radish seed germination and plant growth. As such, the absorption of nutrients can also be improved in the radish plant for the high yield and quality. Anyway, the graphene has great an application potential in the high-efficiency and high-quality cultivation of radish in agricultural production.