Abstract
In this work, the effect of the inoculation of silver-incorporated titanium dioxide nanoparticles (Ag-TiO2 NPs) in spinach seeds was evaluated on certain growth, physiology and phytotoxicity parameters of the plants. This is an important crop for human consumption with high nutritional value due to their low calorie and fat content, providing various vitamins and minerals, especially iron. These NPs were obtained by means of the sol-gel method and heat treatment; the resulting powder material was characterized using X-ray diffraction and scanning electron microscopy and the influence of these NPs on plants was measured by estimating the germination rate, monitoring morphological parameters and evaluating phytotoxicity. The photosynthetic activity of the spinach plants was estimated through the quantification of the Ratio of Oxygen Evolution (ROE) by the photoacoustic technique. Samples of TiO2 powder with particle size between 9 and 43 nm were used to quantify the germination rate, which served to determine a narrower size range between 7 and 26 nm in the experiments with Ag-TiO2 NPs; the presence of Ag in TiO2 powder samples was confirmed by energy-dispersive X-ray spectroscopy. The analysis of variance showed that the dependent variable (plant growth) could be affected by the evaluated factors (concentration and size) with significant differences. The statistical trend indicated that the application of the Ag-TiO2 NPs suspension of lowest concentration and smallest particle size could be a promoting agent of the growth and development of these plants. The inoculation with NPs of 8.3 nm size and lowest concentration was related to the highest average ROE value, 24.6 ± 0.2%, while the control group was 20.2 ± 0.2%. The positive effect of the Ag-TiO2 NPs treatment could be associated to the generation of reactive oxygen species, antimicrobial activity, increased biochemical attributes, enzymatic activity or improvements in water absorption.
Highlights
The demand for healthy food products with nutritional quality has increased [1]
The effect of the inoculation of silver-incorporated titanium dioxide NPs in spinach seeds has a direct dependence on the phytotoxicity, morphology and photosynthetic activity of these plants, depending on the particle size and concentration
In the synthesis of the NPs by sol-gel method, the anatase phase of the titanium dioxide was obtained and the particle size was modified via temperature change in heat treatment
Summary
The demand for healthy food products with nutritional quality has increased [1]. In particular, spinach is consumed mainly for its nutritional content [2], given that it is a low-calorie food that contains protein and a small amount of fat, and that it provides fiber and micronutrients such as vitamin C, vitamin A and minerals, especially iron [3]. Titanium dioxide (TiO2) is one of the most abundant compounds on our planet [7] and it is widely used as a photocatalyst for the conversion of solar energy and for environmental applications due to its characteristics of chemical stability, high refractive index, low cost and lack of toxicity [8]. The potential of this material to promote plant growth and germination, to increase the resistance to stress and to facilitate the absorption of water and oxygen in the seeds has been evaluated recently [9]
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