Biostimulants are materials that when applied in small amounts are capable of promoting plant growth. Nanoparticles (NPs) and nanomaterials (NMs) can be considered as biostimulants since, in specific ranges of concentration, generally in small levels, they increase plant growth. Pristine NPs and NMs have a high density of surface charges capable of unspecific interactions with the surface charges of the cell walls and membranes of plant cells. In the same way, functionalized NPs and NMs, and the NPs and NMs with a corona formed after the exposition to natural fluids such as water, soil solution, or the interior of organisms, present a high density of surface charges that interact with specific charged groups in cell surfaces. The magnitude of the interaction will depend on the materials adhered to the corona, but high-density charges located in a small volume cause an intense interaction capable of disturbing the density of surface charges of cell walls and membranes. The electrostatic disturbance can have an impact on the electrical potentials of the outer and inner surfaces, as well as on the transmembrane electrical potential, modifying the activity of the integral proteins of the membranes. The extension of the cellular response can range from biostimulation to cell death and will depend on the concentration, size, and the characteristics of the corona.

Early blight is a disease that greatly affects Solanaceae, mainly damaging tomato plants, and causing significant economic losses. Although there are methods of biological control, these are very expensive and often their mode of action is slow. Due to this, there is a need to use new techniques that allow a more efficient control of pathogens. Nanotechnology is a new alternative to solve these problems, allowing the creation of new tools for the treatment of diseases in plants, as well as the control of pathogens. The aim of the present investigation was to evaluate the foliar application of selenium and copper in the form of nanoparticles in a tomato crop infested by Alternaria solani. The severity of Alternaria solani, agronomic variables of the tomato crop, and the changes in the enzymatic and non-enzymatic antioxidant compounds were evaluated. The joint application of Se and Cu nanoparticles decreases the severity of this pathogen in tomato plants. Moreover, high doses generated an induction of the activity of the enzymes superoxide dismutase, ascorbate peroxidase, glutathione peroxidase (GPX) and phenylalanine ammonia lyase in the leaves, and the enzyme GPX in the fruit. Regarding non-enzymatic compounds in the leaves, chlorophyll a, b, and totals were increased, whereas vitamin C, glutathione, phenols, and flavonoids were increased in fruits. The application of nanoparticles generated beneficial effects by increasing the enzymatic and non-enzymatic compounds and decreasing the severity of Alternaria solani in tomato plants.

The use of nanoparticles (NPs) has generated an alternative pest control. The objective was to evaluate the insecticidal effect of zinc oxide nanoparticles (ZnO NPs), titanium dioxide nanoparticles (TiO₂ NPs), and their combination on Bactericera cockerelli (Hemiptera: Triozidae) second-stage nymphs under laboratory and greenhouse conditions in tomato. The laboratory research was carried out with the leaf immersion bioassay method under a complete randomized design, and in the greenhouse by direct plant spraying under a randomized block design; in both designs, a control without NPs was added. Mortality was recorded every 24 h for 4 days. Both NPs in the laboratory and greenhouse showed toxicity to B. cockerelli nymphs. Results in the laboratory showed that NPs significantly caused increased mortality of 88, 99, and 100% 96 h after treatment of ZnO NPs, TiO₂ NPs, and their combinations, at 1000, 100, and 250 ppm, respectively. Direct spray of plants in the greenhouse showed low mortality with 27, 32, and 23% after 96 h of ZnO NPs, TiO₂ NPs, and their combinations, at 3000, 500, and 250 ppm, respectively. These results on B. cockerelli control seem promising. Nanoparticles as insecticides are a novel strategy, however, further investigation is required in field tests to obtain suitable efficacy for use in a pest management system.

Selenium (Se) is an essential element of the human diet. Therefore, it is necessary to implement Se in selenium-deficient soils and in the nutrient solution of soilless system culture. Although it is not considered as an essential element for plants, Se provides benefits at the level of redox metabolism, increasing the resistance of plants to various stress factors. The increase of the availability of Se, with the use of biopolymer complexes, was sought in Lactuca sativa var. Great Lakes, grown in substrate pots treated with SeO₂ (5 mg Se/plant), chitosan-polyacrylic acid complex + Se (Cs-PAA + Se) (5 mg Se/plant), and chitosan-polyacrylic acid complex (Cs-PAA). The redox metabolism was modified by increasing the enzymatic activity of catalase and glutathione peroxidase. The use of Cs-PAA + Se biopolymer complexes increased Se up to 24 mg/Kg dry weight (DW) in plant tissues.

Background. Sustainable agriculture promotes the use of mineral and biological origin inputs that act as plant growth stimulants, such as zinc oxide nanoparticles (NPsZnO) and rhizospheric microorganisms, which have positively intervened in the physiological response of plants, due to their unique properties. Objective. To evaluate the effects of NPsZnO applied via foliar and drench, and of rhizospheric microorganisms on the vegetative growth and biomass of tomato plants. Methodology. The doses of nanoparticles were applied at: 0, 10 and 30 mg·L-1 and in microorganisms 0 and 10 spores·mL-1. The variables evaluated were: plant height, stem diameter, number of leaves, leaf area, root length and volume, and total biomass. Results. It was observed that plant height, stem diameter and number of leaves were higher with the interaction of 10 mg·L-1 of NPsZnO and the microbial consortium. The root length decreased 25.88% with the foliar application of 30 mg·L-1 NPsZnO. Root volume decreased 18.49% with the drench application of 30 mg·L-1 NPsZnO and decreased 29.55% with the foliar application of 10 mg·L-1 NPsZnO. The total biomass increased 15.65% and 28.81%, respectively with the foliar application of 30 mgL-1 of nanoparticles and when 30 mg·L-1 of NPsZnO was applied in interaction with the microbial consortium. Implications. Although root length and volume had a negative effect with the application of NPsZnO, plant height, stem diameter, number of leaves and total biomass structural components for fruit production in tomato plants were promoted by the application of NPsZnO in interaction with rhizospheric microorganisms by generating synergism. Conclusion. The dose of the nanoparticles, the application method and the microorganisms in the substrate showed positive synergism in the growth and biomass of tomato plants.

El desarrollo y productividad de los cultivos agrícolas está directamente relacionado con el suministro nutricional que estos reciben. La hipótesis de esta investigación es que la concentración de iones medidos en la solución del suelo, permite evaluar la eficiencia del manejo nutricional y su efecto sobre el cultivo, así, la concentración de iones está condicionada por el aporte mineral y los procesos de intercambio iónico del suelo. El objetivo de ésta investigación, fue medir el efecto de la aplicación continua de cuatro concentraciones de solución nutritiva sobre la concentración de iones en la solución del suelo y la respuesta en el cultivo de tomate bajo invernadero. El ensayo se estableció en suelo calcáreo bajo un diseño de bloques completos al azar con tres repeticiones, con plantas de tomate indeterminado. Los tratamientos fueron cuatro concentraciones con diferente proporción de la solución Steiner modificada para el cultivo de tomate: 1) 50, 2) 75, 3) 100 y 4) 125%, que fueron aplicadas de forma continua por fertirriego. En cada tratamiento se extrajo la solución del suelo y se midió la concentración de los iones NO3-, K+ y Ca+2, el pH y la conductividad eléctrica durante 18 semanas. Al mismo tiempo, se midió la respuesta en el cultivo. La concentración de la solución nutritiva, aplicada de forma constante al cultivo de tomate, presenta una relación directa con la disponibilidad de nutrientes. La solución nutritiva al 125% generó mejor crecimiento, fisiología, calidad comercial y rendimiento agronómico. El calcio fue el único elemento que se detectó en niveles suficientes en la solución del suelo a partir de una concentración de 50% en la solución nutritiva, debido a su alta disponibilidad original del suelo.