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Raspberry has acquired great interest in human health due to its content of bioactive compounds that provide protection against diseases caused by non-communicable diseases. Bioactive compounds are mainly represented by secondary metabolites such as phenols, anthocyanins, and flavonoids. Biostimulants and elicitors are substances or microorganisms that provide protection and defence to the physiological processes of plants. The present study evaluated the effect of two elicitors (hydrogen peroxide, salicylic acid) and three biostimulants (humic and fulvic acids, glutamic acid, seaweed extracts) on the content of bioactive compounds in raspberry fruits, agronomic and fruit yield parameters in plants. Hydrogen peroxide increased the content of bioactive compounds such as flavonoids, anthocyanins, omega 3 and oleic acid. Salicylic acid increased the content of flavonoids, anthocyanins, and citric acid in raspberry fruits; the number of fruit loaders and fruits per plant was also increased. Humic and fulvic acids, glutamic acid, and glutamic acid combined with seaweed extracts increased the content of flavonoids and anthocyanins, without affecting growth parameters and fruit yield. Glutamic acid and seaweed extracts were the only treatments that increased the content of palmitic acid, while seaweed extracts increased °Brix content in fruits.

Blueberry production and fruit quality face increasing challenges under current climate change scenarios. Therefore, sustainable strategies such as the use of biostimulants, which have shown beneficial effects that enhance productivity and quality, are needed. This study evaluated the effect of foliar and drench preharvest applications of biostimulants on the growth, yield, and fruit quality of blueberry. The experiment was conducted using plants grown in coconut fiber under greenhouse conditions in a randomized factorial design with three factors: biostimulant, application method, and application dose. The biostimulants tested included melatonin, salicylic acid, glutamic acid, silicon, and yeast extract, applied biweekly from anthesis to fruit maturity. Growth parameters, yield, size, color, and quality traits were measured. The drench application of 100 µM melatonin resulted in the highest yield and plant height, whereas stem diameter increased mainly with 100 µM foliar melatonin. Foliar application of 1000 mg L⁻¹ glutamic acid significantly enhanced the SPAD index. Fruit weight, width and height were superior under 4 mM salicylic acid applied via drench and 500 mg L⁻¹ glutamic acid applied foliar. The width/height ratio reached its highest value with 100 µM foliar melatonin. Foliar silicon at 5 g L⁻¹ increased fruit lightness, while 3 g L⁻¹ yeast extract applied via drench enhanced chroma, with no significant differences in hue. All biostimulants improved fruit firmness; additionally, foliar silicon increased total soluble solids, and 10 g L⁻¹ yeast extract applied foliar enhanced anthocyanin content. Biostimulants applications improved growth, yield, and fruit quality, supporting their potential for sustainable blueberry production.

Iodine is an essential trace nutrient for humans; its deficit can affect motor and cognitive development. Biofortifying crops with iodine is a way of promoting the adequate intake of this element. The uses of chitosan-iodine complexes for crop biofortification have not been previously studied. The present work evaluated the effects of KIO3 and KI salts, chitosan-KIO3 complex (Cs-KIO3), and chitosan-KI complex (Cs-KI) application on lettuce, with a chitosan-only treatment as a control and water as the absolute control. Each treatment involved the application of 0, 5, and 25 mg I kg−1 soil applied before transplanting or 25 mg I kg−1 soil applied as split doses of 12.5 mg kg−1, once immediately before transplanting and the second application 15 days later. Single application of Cs-KIO3 at 5 and 25 mg I kg−1 increased lettuce biomass while the split-dose application (SDA) of Cs-KI (25 mg I kg−1) led to a decrease in biomass. Maximum accumulation of iodine in lettuce was observed after the application of KIO3 (25 mg I kg−1) in two parts. This study shows that the use of chitosan complexes, especially Cs-KIO3, may be a viable alternative for crop biofortification with iodine without affecting crop yields.

Selenium (Se) is a beneficial nutrient for plants and its application as seed priming is associated with positive effects on their growth. The use of Se occurs in ionic or nanometric form, however, another possible use is in micrometric form, which to our knowledge has not been studied in plants. The objective of the study was to evaluate the seed priming of cucumber (Cucumis sativus L.) with sodium selenite (Na2SeO3), nanoparticles (SeNPs) and Se microparticles (SeMPs) at concentrations of 0, 0.1, 0.5, 1.0, 1.5 and 3.0 mg L-1 of Se, for each of the mentioned forms. Growth, biomass, vigor, biomolecules and nutrients were evaluated in cucumber seedlings grown in a growth chamber for 15 days. The results showed increases in seedling length and biomass for all Se forms, which was reflected in increases in vigor indices from 21.42% to 27.72% for vigor index 1 (length) and from 16.96% to 34.5% for vigor index 2 (biomass), with SeMPs standing out at 1.0 and 1.5 mg L-1. Regarding pigments, variable effects were observed, where some treatments did not modify the concentration of chlorophylls and carotenoids (SeMPs) and others negatively affected (SeNPs and Na2SeO3). Reduced glutathione increased from 13.48% to 31.59%, with SeMPs standing out at 1.0 and 1.5 mg L-1. Phenols, flavonoids, proteins, S, K and Mg were also increased with the different Se materials; however, P, Ca, Fe, Zn, Cu and Mn decreased with some Se treatments. The results indicate that it is advisable to apply Na2SeO3, SeNPs and SeMPs, mainly SeMPs at 1.0 and 1.5 mg L-1.

Since the fruit of the Capsicum annuum L. var. glabriusculum (Dunal) Heiser and Pickergil (chiltepín pepper) has a low germination rate, we sought to determine whether using an aqueous biochar extract could improve this. Germination tests were performed out in Petri dishes, using wild chiltepín pepper seeds collected in Sonora, México, which were exposed for 24 h to aqueous extracts of coconut shell biochar (CSBA) at different doses (0.05, 0.10, 0.25, 0.50, 0.75, and 1.00%, w/v) and a control comprising deionized water. In addition to quantifying the germination rate, we determined the physical quality, viability, imbibition, electrical conductivity, seed pH, and capsaicin content. The fast green test showed an ideal physical quality (p = 0.5475), an imbibition rate > 65% (p > 0.05), and high viability 98.4% (p > 0.05). The wild chiltepín pepper seeds exposed to the CSBA0.05 and CSBA0.25 treatments increased the percentage germination rate (p < 0.001) to 80.9% and 71.7%, respectively. A higher percentage of normal seedlings resulted from CSBA0.05, CSBA0.10 and CSBA1.00 (p < 0.01), and a greater shoot length was obtained with CSBA0.05 (p < 0.01). The exposure of wild chiltepín seeds to aqueous CSBA for 24 h at low doses (CSBA0.05 and CSBA0.25) increase the germination rate, while CSBA0.05 could enhance early seedling growth.

Chitosan is a natural polymer, which has been used in agriculture to stimulate crop growth. Furthermore, it has been used for the encapsulation of nanoparticles in order to obtain controlled release. In this work, the effect of chitosan–PVA and Cu nanoparticles (Cu NPs) absorbed on chitosan–PVA on growth, antioxidant capacity, mineral content, and saline stress in tomato plants was evaluated. The results show that treatments with chitosan–PVA increased tomato growth. Furthermore, chitosan–PVA increased the content of chlorophylls a and b, total chlorophylls, carotenoids, and superoxide dismutase. When chitosan–PVA was mixed with Cu NPs, the mechanism of enzymatic defense of tomato plants was activated. The chitosan–PVA and chitosan–PVA + Cu NPs increased the content of vitamin C and lycopene, respectively. The application of chitosan–PVA and Cu NPs might induce mechanisms of tolerance to salinity.

Iodine is not considered essential for land plants; however, in some aquatic plants, iodine plays a critical role in antioxidant metabolism. In humans, iodine is essential for the metabolism of the thyroid and for the development of cognitive abilities, and it is associated with lower risks of developing certain types of cancer. Therefore, great efforts are made to ensure the proper intake of iodine to the population, for example, the iodization of table salt. In the same way, as an alternative, the use of different iodine fertilization techniques to biofortify crops is considered an adequate iodine supply method. Hence, biofortification with iodine is an active area of research, with highly relevant results. The agricultural application of iodine to enhance growth, environmental adaptation, and stress tolerance in plants has not been well explored, although it may lead to the increased use of this element in agricultural practice and thus contribute to the biofortification of crops. This review systematically presents the results published on the application of iodine in agriculture, considering different environmental conditions and farming systems in various species and varying concentrations of the element, its chemical forms, and its application method. Some studies report beneficial effects of iodine, including better growth, and changes in the tolerance to stress and antioxidant capacity, while other studies report that the applications of iodine cause no response or even have adverse effects. We suggested different assumptions that attempt to explain these conflicting results, considering the possible interaction of iodine with other trace elements, as well as the different physicochemical and biogeochemical conditions that give rise to the distinct availability and the volatilization of the element.

Sulfur is an essential element in determining the productivity and quality of agricultural products. It is also an element associated with tolerance to biotic and abiotic stress in plants. In agricultural practice, sulfur has broad use in the form of sulfate fertilizers and, to a lesser extent, as sulfite biostimulants. When used in the form of bulk elemental sulfur, or micro- or nano-sulfur, applied both to the soil and to the canopy, the element undergoes a series of changes in its oxidation state, produced by various intermediaries that apparently act as biostimulants and promoters of stress tolerance. The final result is sulfate S+6, which is the source of sulfur that all soil organisms assimilate and that plants absorb by their root cells. The changes in the oxidation states of sulfur S0 to S+6 depend on the action of specific groups of edaphic bacteria. In plant cells, S+6 sulfate is reduced to S−2 and incorporated into biological molecules. S−2 is also absorbed by stomata from H2S, COS, and other atmospheric sources. S−2 is the precursor of inorganic polysulfides, organic polysulfanes, and H2S, the action of which has been described in cell signaling and biostimulation in plants. S−2 is also the basis of essential biological molecules in signaling, metabolism, and stress tolerance, such as reactive sulfur species (RSS), SAM, glutathione, and phytochelatins. The present review describes the dynamics of sulfur in soil and plants, considering elemental sulfur as the starting point, and, as a final point, the sulfur accumulated as S−2 in biological structures. The factors that modify the behavior of the different components of the sulfur cycle in the soil–plant–atmosphere system, and how these influences the productivity, quality, and stress tolerance of crops, are described. The internal and external factors that influence the cellular production of S−2 and polysulfides vs. other S species are also described. The impact of elemental sulfur is compared with that of sulfates, in the context of proper soil management. The conclusion is that the use of elemental sulfur is recommended over that of sulfates, since it is beneficial for the soil microbiome, for productivity and nutritional quality of crops, and also allows the increased tolerance of plants to environmental stresses.

Saline stress severely affects the growth and productivity of plants. The activation of hormonal signaling cascades and reactive oxygen species (ROS) in response to salt stress are important for cellular detoxification. Jasmonic acid (JA) and the enzyme SOD (superoxide dismutase), are well recognized markers of salt stress in plants. In this study, the application of chitosan-polyvinyl alcohol hydrogels (Cs-PVA) and copper nanoparticles (Cu NPs) on the growth and expression of defense genes in tomato plants under salt stress was evaluated. Our results demonstrate that Cs-PVA and Cs-PVA + Cu NPs enhance plant growth and also promote the expression of JA and SOD genes in tomato (Solanum lycopersicum L.), under salt stress. We propose that Cs-PVA and Cs-PVA + Cu NPs mitigate saline stress through the regulation of oxidative and ionic stress.

Tomato crop is valuable worldwide thanks to its commercial and nutritional value, which plays a very important role in the human diet. However, in arid areas, tomato crops can be found with high salt content. Salinity is a major problem for agriculture, as it decreases productivity, lowers economic yields, and induces soil erosion. The application of silicon has been observed to increase tolerance to abiotic stress and specifically to salt stress. Therefore, the aim of this study is to evaluate the application of K2SiO3 and SiO2 nanoparticles (SiO2 NPs) on the growth, antioxidant content, and tolerance to saline stress of tomato plants. Plant growth, fruit quality parameters (pH, titratable acidity, total soluble solids, firmness), antioxidant capacity (ABTS, DPPH), enzymatic (SOD, PAL, APX, CAT, GPX) and non-enzymatic (flavonoids, phenols, vitamin C, β-carotene, lycopene) antioxidant compounds, chlorophylls, proteins, and H2O2 were evaluated. The application of SiO2 NPs at 500 mg L−1 had positive effects on the plants that were not subjected to stress, increasing the average fruit weight, fruit yield, and chlorophyll, phenol, glutathione, and GPX activity. Meanwhile, in plants under salt stress, it helped to maintain the concentration of chlorophylls, GSH, PAL activity, and vitamin C. The application of SiO2 NPs is more effective than K2SiO3 at inducing positive responses in tomato plants subjected to stress by NaCl.