Ulva ohnoi is a cosmopolitan green seaweed with commercial potential given the biomass that may be generated. We evaluated the effects of substrate changes induced by U. ohnoi application on the vegetative response of tomato plants under greenhouse conditions. First, the decomposition dynamics and N release of the dry seaweed biomass were studied using the litterbag method. Subsequently, we evaluated the effect of seaweed powder (SP) or seaweed extract (SE) applications on substrate and plant growth. Additionally, the growth parameters responses evaluated were related to the changes in substrate properties associated with each treatment. The results showed that the dry seaweed biomass has a rapid rate of degradation (k = 0.07 day⁻¹) and N release (k = 0.024 day⁻¹). The SP application improved the physicochemical and biological characteristics of the substrate by increasing the availability of minerals, the fungi:bacteria ratio, and the growth morphophysiological parameters (length, area, dry and fresh weight), chlorophyll and mineral content. In contrast, SE treatment showed a positive effect on the root, mineral content, and soil microbes. This study highlights the agricultural potential of U. ohnoi powder as an alternative supplement that supports nutrition and promotes the vegetative growth of plants cultivated in soilless horticultural systems.

The main challenge facing the agricultural sector today is to ensure continued access to enough nutritious food with minimal environmental impact. Therefore, the search for sustainable and effective methods to stimulate crop yield and quality is a priority. Plants are emerging as an attractive local resource for biostimulant extracts due to their abun[1]dant biomass and high content of bioactive compounds. However, the factors that support the implementation of botanical extracts as alternative bioproducts to reduce dependence on agrochemicals are not yet fully understood. This review aimed to analyze the available information on the potential use of botanical extracts as biostimulants for Mexican agriculture. An updated overview of the definition and regulation of agricultural biostimulants worldwide and in Mexico is provided. In addition, research trends on the biostimulant properties of extracts derived from Mexican plants related to the species used as raw material, extraction methods, modes of application, and types of crops evaluated are analyzed. Finally, the effects and mechanisms of action of botanical extracts on crop plants are discussed, and future research needs to optimize their application in agricultural production.

In the last decade, interest in the use of seaweed and seaweed-derived products in horticulture has grown due to their great potential as biostimulants for increasing yields and improving food quality in multiple crops. A greenhouse experiment was conducted to investigate the effects of the application of the green seaweed Ulva ohnoi (either as a seaweed suspension [SWS] or seaweed extract [SWE]) on the yield, size, shape, and nutritional quality (i.e., proximate composition and dietary antioxidant content) of tomato fruits (Solanum lycopersicum L. cv. Rio Fuego). A total of 36 tomato plants were potted individually and organized into three experimental groups: SWS (plants drenched with 250 mL of seaweed suspension [2.0%]), SWE (plants drenched with 250 mL of seaweed extract [0.2%]), and control (plants irrigated with water). Each treatment included three replications. The fruits harvested (66%) from SWS-treated plants were produced during the earliest harvest stages. In contrast, the fruits harvested from SWE-treated plants (82%) and control plants (77%) were produced during the late and very late harvest stages. Notably, SWS application significantly enhanced the number of fruits harvested per plant, average fruit weight, yield (kg/plant), number of seeds per fruit, and fruit size. Furthermore, tomato fruits from plants treated with either SWS or SWE exhibited higher percentages of protein, fat, crude fiber, dry matter, and total soluble solids, as well as lower acidity and reduced total carbohydrate content, compared to the control. The antioxidant metabolites in tomatoes, including lycopene, β-carotene, flavonoids, and phenolic acids, increased following the application of SWS and SWE, while anthocyanin and ascorbic acid contents increased only in SWS-treated plants. These results demonstrate that both forms of U. ohnoi application have biostimulating effects on tomato. In particular, the use of SWS shows great potential as a strategy to enhance tomato fruit productivity and quality in sustainable horticultural systems.

Algae-derived products have great potential as crop biostimulants due to their multiple beneficial effects at different stages of plant development. Green seaweeds of the genus Ulva are well suited for this purpose because they are widely distributed and grow rapidly in a wide range of conditions. In this study, a greenhouse experiment was conducted to evaluate the effects of dry seaweed powder (DSP) and liquid seaweed extract (LSE) of Ulva ohnoi on the reproductive development of tomato plants. The experiment included three treatments: 1) plants treated with 5 g of DSP, 2) plants treated with 250 mL of LSE, and (3) control plants (without algae). The reproductive parameters, chlorophyll content, and mineral composition were measured during the flowering and early fruiting periods. The application of DSP was the most effective treatment in promoting early flowering and significantly increased the number of buds (103%), flower clusters (55%), flowers (61%), and fruits (45%) per plant. Furthermore, the DSP-treated plants exhibited an enhancement in the levels of chlorophyll and nutrients in the plants and fruits. The results of the current work show that the application of U. ohnoi in its natural form (dry powder) stimulates the reproductive development of crop tomato. This represents a sustainable and natural alternative to synthetic inputs that growers can incorporate into horticultural production to improve yield attributes.