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.

Seaweeds are used in traditional agriculture practices because of their beneficial effects. Recently, the rising demand for organically grown foods has amplified the use of organic fertilizers such as seaweed extracts. Despite their beneficial effects, few studies have reported information about compounds in seaweed extracts that are responsible for these benefits. Thus, the aim of this study was to evaluate the potential relationships between the components and secondary metabolites in four seaweed liquid extracts from Eisenia arborea, Macrocystis pyrifera, Padina caulescens, and Sargassum horridum and their biostimulant activity through changes in the germination, growth, and protein content of tomato seedlings (Solanum lycopersicum). The E. arborea and S. horridum extracts showed similar compositions (ash, organic carbon, bicarbonates, and chlorides), minerals (Ca, Fe, and Cu) and secondary metabolites (triterpenes and saponins), albeit with different component concentrations. The chemical composition of the P. caulescens extract was significantly different from those of the other extracts; it was characterized by high levels of total nitrogen, phenols, and carbohydrates. Almost all seaweed extracts had beneficial effects on seed germination and seedling length, except the S. horridum extract that inhibits germination. The hierarchical clustering plots and principal component analysis indicated that germination and protein content are related to the presence of sterol. Shoot length was closely related to mineral levels (K, Zn, B, Na) and the C:N ratio, whereas radicle length was closely related to the content of nitrogen, carbohydrates, phenols, and flavonoids in the seaweed extracts. However, the underlying mechanisms are still unclear and require further studies.

The use of extracts derived from different plants has gained popularity as an alternative option to manage weeds and support phenological development in plants. One of the main problems facing agricultural production is the intensive application of chemical fertilizers that harm the environment. This study investigated the biostimulant effects of the aqueous extracts of Verbesinasphaerocephala and Verbesinafastigiata on the germination and growth of tomato (Solanum lycopersicum) and American cucumber (Cucumis sativus) seedlings. The aqueous extracts of both species of Verbesina were tested at concentrations of 0.5 and 1%. Seed germination and seedling development under nursery conditions were evaluated. The seed germination percentage was reduced in all treatments with the extracts of both Verbesina species when compared to that of the control treatment, which was considered an allelopathic effect. However, seedling growth in pots showed different behavior, with the extracts beneficially affecting certain agronomic variables, such as root and leaf length. The results suggest potential uses for V. sphaerocephala and V. fastigiata extracts, although a greater range of action may be experienced through the effects of certain molecules on weed growth. Additional studies with chemical approaches are necessary to better direct the uses and applications of Verbesina biomolecules, as they also functioned as growth promoters.

Daminozide (B-Nine) it is a plant growth regulator, is translocated from the leaves to the stem to avoid elongation and produce more compact plants and uniform growth and vigor. For the cultivation of Lisiathus the information of the damonizide application is scarce despite of great marketing potential, so the objective of this study was to evaluate the effect of daminozide on the vegetative growth and flowering of Lisianthus grown in pot. Granulated Lisianthus seeds were germinated and transplanted into pots under nursery conditions. Three foliar applications of daminozide were realized; two applications in vegetative stage and one in flowering, adding three concentrations in each of them (0.5, 1.0 and 1.5 ml L–1) were used and water was applied as a control during the vegetative and flowering phases. The applications of daminozide at 1.0 and 1.5 ml L–1 were optimal for the vegetative development in Lisianthus (plant height – 15 cm, size of the internodes – 2.5 cm, number of branches – 3, width and length of the leaves – 3 cm and 6.5 cm), while the dose of 0.5 ml L–1 was favorable for all flowering stages (beginning of flowering – 182 buttons, sepals closed and larger than the petals – 53), visible petals larger than the sepals – 25, floral opening and full flowering – 3 flowers per plant). Based on these results, the application of B-Nine at low concentrations (0.5 and 1 ml L–1) is recommended for the development of Lisianthus in pots.

Sustainable alternatives to herbicides, agrochemicals, and other synthetic molecules are imperative for the ecological sustainability in the line of United Nations Sustainable Development Goals (SGD) goals. Natural aqueous extracts from different plant species are important sources of biomolecules that can be used to holistically manage crops by improving germination and plant development. The objective of this study was to evaluate the application of two aqueous extract preparations of Verbesina sphaerocephala on the germination and development of tomato and mung bean seedlings. Infusion and maceration extracts were prepared using V. sphaerocephala leaves at different concentrations (0.25, 0.75, and 1.5 g/l). The effects on seed germination and seedling development were evaluated under nursery conditions. The germination percentage of tomato seeds was significantly reduced following the application of all extracts, which was considered an allelopathic effect. The opposite results were observed in mung bean seeds. Seedling development also differed between species following extract application, although the development of certain agronomic variables, such as stem height, root length, and fresh weight, were favored in both in tomato and mung bean. From the study, it may be conclude that V. sphaerocephala extracts delay germination during the first three days of tomato growth, however, they promote optimum seedling development both in tomato and mung bean.

Introducción. Uno de los principales problemas de importancia económica en la producción de plantas ornamentales es la alta incidencia de enfermedades. Fusarium oxysporum es un patógeno cosmopolita capaz de afectar cualquier etapa fenológica de plantas de lisianthus. Dado que el uso de fungicidas químicos puede ser ineficaz contra patógenos de suelo debido a la resistencia que estos desarrollan, se ha incrementado el interés por alternativas sostenibles, como el uso de bacterias promotoras de crecimiento vegetal (PGPR) y los extractos vegetales para mejorar la respuesta de defensa de las plantas. Objetivo. Evaluar el efecto de Bacillus subtilis y un extracto etanólico de Verbesina sphaerocephala para el control de Fusarium oxysporum en el cultivo de lisianthus. Métodos. Se aisló e identificó el patógeno a partir de material vegetal con síntomas de enfermedad y se realizaron pruebas in vitro colocando F. oxysporum en medio PDA con los siguientes tratamientos: T1. Baktillis (B. subtilis), T2. Cineto 600 pH (Tiabendazol), T3. KerKab (fungicida biológico), T4: Extracto etanólico de V. sphaerocephala (4000 ppm), T5: Extracto etanólico de V. sphaerocephala (4 000 ppm) + Baktillis, y T6: Testigo. Se midió el crecimiento diario del micelio durante nueve días y se calculó el porcentaje de inhibición del crecimiento radial, realizando cada evaluación por triplicado. Resultados y discusión. Los resultados obtenidos mostraron que el T1 inhibió el 100 % del crecimiento micelial, similar al efecto que tuvo el T2, el T4 tuvo un efecto del 53.42 %, mientras que el T5 mostró un porcentaje de inhibición del 75.64 %. Estos hallazgos coinciden con lo reportado por Rodríguez Castro et al. (2020); quienes destacan la presencia de compuestos antifúngicos en extractos vegetales de diferentes plantas. Conclusión. El uso de bioestimulantes como B. subtilis y extractos de V. sphaerocephala representa una alternativa sustentable para reducir los problemas fitosanitarios en lisianthus y disminuir las pérdidas económicas asociadas, ofreciendo un enfoque integrado y ecológico para el manejo de enfermedades fúngicas en cultivos ornamentales.