Biostimulants constitute an emerging group of crop management products used to enhance productivity under abiotic stress conditions. The ability of some biostimulant products, such as seaweed extracts (SE), to enhance crop tolerance to salinity stress has been documented. SE contain a series of bioactive compounds and signaling molecules, as well as mineral and organic nutrients, that greatly benefit plants. A greenhouse experiment was conducted in order to evaluate SE-mediated tolerance mechanisms in tomato plants under salinity stress. The experiment was divided into two developmental phases (vegetative and reproductive) and included four treatments: control (plants with neither treatment), SE (plants treated with seaweed extract), NaCl (plants irrigated with 300 mM NaCl), and SE + NaCl (plants treated with seaweed extract and irrigated with 300 mM NaCl). Tomato plants treated with the SE from Padina gymnospora showed an increase in root and shoot length (18 cm and 13 cm), root and shoot area (33 cm² and 98 cm²), and shoot and root fresh weight (1.0 and 3.8 g) under the control and salinity stress conditions. The decrease in productivity (number of fruits) associated with salinity stress was reduced from 28.7% to only 3.4% in SE-treated plants. The positive effects of SE application also included early flowering and enhanced fruit weight and quality. Our findings suggest that optimized photosynthetic performance and antioxidant defense systems (proline, total phenols, and flavonoids) appear to be major factors modulating SE responses to salinity tolerance in tomato plants with promising agricultural applications.

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.

Agave tequilana Weber cultivar ‘Chato’ represents an important genetic supply of wild severely in decline populations of ‘Chato’ for breeding and transformation programs. In this work, the indirect somatic embryogenesis and cryopreservation of Somatic Embryos (SEs) were investigated using the ‘Chato’ cultivar as a study case. Methods: Embryogenic calli were induced by the cultivation of 1 cm of young leaves from in vitro plants on MS semisolid medium supplemented with 24.84, 33.13, 41.41, 49.69, and 57.98 μM 4-amino-3,5,6-trichloro-2- pyridinecarboxylic acid (picloram) in combination with 2.21, 3.32, and 4.43 μM 6-benzylaminopurine (BAP). The origin and structure of formed SEs were verified by histological analysis. Cryopreservation studies of SEs were performed following the V-cryoplate technique and using for dehydration two vitrification solutions (PVS2 and PVS3). Results: The highest average (52.43 ± 5.74) of produced SEs and the Embryo Forming Capacity (estimated index 52.43) were obtained using 49.69 µM picloram and 3.32 µM BAP in the culture medium. The highest post-cryopreservation regrowth (83%) and plant conversion rate (around 70%) were achieved with PVS2 at 0 °C for 15 min. Conclusion: Our work provides new advances about somatic embryogenesis in Agave and reports the first results on cryopreservation of SEs of this species.

Greenhouse-grown plants of Agave tequilana Weber var. azul were inoculated with Erwinia carotovora, the causal agent of stem soft rot. We investigated the laser-induced fluorescence (LIF) of agave plants to determine whether LIF can be used as a noninvasive sensing tool for pathological studies. The LIF technique was also investigated as a means of detecting the effect of the polyamine biosynthesis inhibitor β-hydroxyethylhydrazine as a bactericide against the pathogenic bacterium Erwinia carotovora. A He-Ne laser at 632.8 nm was used as the excitation source, and in vivo fluorescence emission spectra were recorded in the 660–790-range. Fluorescence maxima were at 690 and 740 nm. The infected plants that were untreated with the bactericide showed a definite increase in fluorescence intensity at both maxima within the first three days after infection. Beginning on the fifth day, a steady decrease in fluorescence intensity was observed, with a greater effect at 740 than at 690 nm. After 30 days there was no fluorescence. The infected plants that had been treated with the bactericide showed no significant change in fluorescence compared with that of the uninfected plants. The ratio of fluorescence intensities was determined to be F 690 nm/F 740 nm for all treatments. These studies indicate that LIF measurements of agave plants may be used for the early detection of certain types of disease and for determining the effect of a bactericide on bacteria. The results also showed that fluorescence intensity ratios can be used as a reliable indicator of the progress of disease.

A. marmorata is the raw material used for tepextate mescal production but is classified as an endangered species. In the present study, we obtain and multiply clonal lines of Agave marmorata Roezl by selecting seedlings derived from seeds. Ten seedlings from two lots of 400 germinated seeds were selected for axillary bud proliferation induced by BAP 5 mg/L in vitamin-free Murashige and Skoog’s medium. Differences in shoot numbers, heights and senescent tissue formation were observed. Notably, the AM32 line formed 84 shoots and presented low senescent tissue after 60 d of culture. We also selected the AM31 and AM33 clonal lines. Four-month shoots were extracted with 80% methanol in water to determine the total content of saponins, flavonoids, and phenolic acids and compare the three clonal lines. Some bioactive molecules were identified using HPLC techniques and MALDI-TOF mass spectrometry none showed significant differences in content. Additionally, plants derived from the clonal lines were inoculated with four endophytic bacteria. Among these, Achromobacter xylosoxidans supported plant growth of AM32. A notable effect of plant death was observed after inoculation with Enterobacter cloacae, an endophyte of A. tequilana. Additionally, Pseudomonas aeruginosa, an endophyte from A. marmorata, reduced biomass. Our results demonstrate the incompatibility of A. marmorata to E. cloacae and specialization between the host plant and its endophytes. The compatibility of the plant-endophyte could be exploited to boost the establishment and stability of mutualisms to benefit plant development, stress tolerance and pathogen resistance. The differences in multiplication capacity, stable tissue formation, and endophyte biotization responses may indicate genetic variability. Clonal selection and micropropagation from seed-derived plants could contribute to conserving the endangered A. marmorata plant for reforestation in their natural habitats, thus, assuring mass propagation for sustainable industrial production of mescal, bioactive compounds, and prebiotics.