Currently, the use of biostimulants in agriculture is a tool for mitigating certain environmental stresses. Brown algae extracts have become one of the most important categories of biostimulants in agriculture, and are derived from the different uses and positive results obtained under optimal and stressful conditions. This study aimed to examine the efficacy of a foliar application of a hydroalcoholic extract of Sargassum spp. and two controls (a commercial product based on Ascophyllum nodosum and distilled water) with regard to growth, the antioxidant system, and the expression of defense genes in tomato seedlings grown in nonsaline (0 mM NaCl) and saline (100 mM NaCl) conditions. In general, the results show that the Sargassum extract increased the growth of the seedlings at the end of the experiment (7.80%) compared to the control; however, under saline conditions, it did not modify the growth. The Sargassum extract increased the diameter of the stem at the end of the experiment in unstressed conditions by 14.85% compared to its control and in stressful conditions by 16.04% compared to its control. Regarding the accumulation of total fresh biomass under unstressed conditions, the Sargassum extract increased it by 19.25% compared to its control, and the accumulation of total dry biomass increased it by 18.11% compared to its control. Under saline conditions, the total of fresh and dry biomass did not change. Enzymatic and nonenzymatic antioxidants increased with NaCl stress and the application of algal products (Sargassum and A. nodosum), which was positively related to the expression of the defense genes evaluated. Our results indicate that the use of the hydroalcoholic extract of Sargassum spp. modulated different physiological, metabolic, and molecular processes in tomato seedlings, with possible synergistic effects that increased tolerance to salinity.

The use of elicitors or biostimulants such as salicylic acid (SA) is an emerging novel practice to improve the yield and quality of crops since it plays an important role in the regulation of various physiological and metabolic processes. The objective of this research was to study the effect of the foliar application of SA on the nutraceutical quality and yield of tomato fruits. A completely randomized experimental design with 10 repetitions was used. SA was applied at five doses (0.025 mM, 0.05 mM, 0.075 mM, 0.1 mM, and 0.125 mM) every 15 days through foliar sprays after transplantation, accumulating seven applications through the cycle. The response variables were yield (total fruit weight per plant), fruit parameters (weight, diameter, firmness, and total soluble solids), percentage of weight loss, and nutraceutical quality. The obtained results suggest that the foliar spraying of SA improves the yield and biosynthesis of phytochemical compounds in tomato fruits, compared to control plants. According to the results, it is advisable to use the dose of 0.125 mM of SA since it has a higher content of bioactive compounds without compromising yield.

The growing demand for food production and increasing stress scenarios increase the crucial need for sustainable alternatives to achieve increased crop yield and quality without affecting the environment. The use of brown macroalgae, being a renewable resource, is a promising option with various application options in agricultural systems, mainly in the form of extracts, direct applications, and compost. Brown algae are a source of active biomolecules and minerals that are currently used as agricultural biostimulants, since they increase crop productivity. This type of biostimulants derived from brown algae improve seed germination, increase the accumulation of plant biomass by accelerating cell division and elongation, activating the antioxidant system of plants, making them more resistant to stress, and contributes to the absorption and translocation of nutrients present in the soil. These products are also compatible with other agricultural inputs, such as synthetic fertilizers and pesticides, which makes them ideal for comprehensive applications and maintaining a balance in agroecosystems. This review incorporates fundamental and applied aspects of brown seaweeds that impact yields, biochemical quality, physiology, stress mitigation, and soil properties. Based on the above, the review is divided into different Sections that show the formulation of brown seaweed products; their effect on crop yield, quality, and physiology; their effect on biotic and abiotic stress mitigation; and their impact on soil physical, chemical, and biological properties.

La concentración de iones en la solución nutritiva en sistema sin suelo tiene un impacto directo en el rendimiento y calidad de los cultivos. El objetivo de esta investigación fue evaluar el efecto de la conductividad eléctrica de la solución nutritiva sobre la biomasa, pigmentos y compuestos nitrogenados en el cultivo de lechuga. Se utilizo un diseño experimental en bloques completos al azar con cinco tratamientos (1, 1.5, 2, 2.5 y 3 dS m-1) y nueve repeticiones. Se determinó la biomasa total (fresca y seca) y la acumulación de clorofilas, carotenoides, proteínas, aminoácidos, glutatión reducido y capacidad antioxidante hidrofílica ABTS. Los resultados indican que la conductividad eléctrica de la solución nutritiva que mejoró la acumulación de biomasa fue la de 2.5 dS m-1, la de 2 dS m-1 incrementó la concentración de proteínas y aminoácidos, mientras que la conductividad eléctrica de 3 dS m-1 mejoró la concentración de pigmentos, glutatión reducido y aumentó la capacidad antioxidante hidrofílica ABTS, pero disminuyó el rendimiento. El manejo adecuado de la conductividad eléctrica de la solución nutritiva es un factor de basta importancia en la mejora del rendimiento y calidad de los cultivos en sistemas sin suelo.

Currently, biostimulants in the horticultural sector are a tool that is being used to improve the yield and quality of vegetables under optimal and stressful growth conditions. In the present study, we evaluate the effects of foliar application of a hydroethanolic extract of Sargassum spp., a commercial extract based on Ascophyllum nodosum, and a control with distilled water on growth and biomass, stomatal conductance, photosynthetic pigments, enzymatic and non-enzymatic antioxidants, protein content, and the expression of defense genes in tomato plants (Solanum lycopersicum L.) without stress and with high-temperature stress (45 °C). The results showed that Sargassum spp. extract only increased the height of tomato plants under stress-free conditions (2.71%) in the last evaluation. The aboveground and total dry biomass of the plants were increased by Sargassum spp. extract under stress-free conditions by 9.56 and 8.58%, respectively. Under stress conditions, aboveground dry biomass was increased by 6.66% by Sargassum spp. extract. Stomatal conductance, photosynthetic pigments, protein content, enzymatic and non-enzymatic antioxidants, and defense gene expression of tomato plants were positively modified with the use of Sargassum spp. and A. nodosum extract under high-temperature stress conditions. Under stress-free conditions, the described variables were positively modified except for gene expression, where some genes were expressed and others were repressed. The results indicate that extracts of Sargassum spp. and A. nodosum are effective in mitigating high-temperature stress, making their use a promising alternative for inducing resistance in plants to the daily adversities of climate change.

El ácido indol-3-acético (AIA) es la principal auxina en las plantas y controla varios procesos fisiológicos y bioquímicos como el alargamiento y la división celular, la diferenciación de tejidos, las respuestas a la luz y la gravedad, y la respuesta al estrés biótico y abiótico. Por tanto, el objetivo del trabajo fue evaluar el efecto de la aplicación foliar de altas concentraciones de AIA (0.5, 1, 2 y 3 mM) más un testigo (agua destilada) sobre variables agronómicas y metabolómicas en plántulas de melón. Los resultados indican que para las variables agronómicas, el AIA a una concentración de 0.5 mM mejoró la altura en un 20.98 %, en comparación con el control, y a partir de 1 mM comenzó a disminuir a medida que aumentaba la concentración de AIA. Para la biomasa fresca y seca total, se puede observar que el control y la concentración de 0.5 mM fueron estadísticamente iguales, sin embargo, a partir de 1 mM la biomasa comenzó a disminuir a medida que aumentaba la concentración de AIA. En cuanto a las biomoléculas, se observa un aumento de clorofilas (a, b y total), flavonoides, capacidad antioxidante y proteínas a medida que aumenta la concentración de AIA. Los tratamientos con AIA a 0.5, 1 y 2 mM incrementaron la concentración de carotenoides en 11.76, 11.76 y 8.82 %, respectivamente, en comparación con el control, sin embargo, con la concentración 3 mM comenzaron a disminuir, pero aun así superaron al control. Se concluye que partir de la concentración de 1 mM de AIA comenzaron a disminuir las características agronómicas de las plántulas, por lo tanto, es recomendable que se usen concentraciones por debajo de 0.5 mM de AIA para poder dilucidar cómo funcionan concentraciones inferiores. En cuanto a las variables metabolómicas, aumentaron conforme se elevó la concentración de AIA.