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The impact of nanotechnology in the field of agricultural sciences creates the need to study in greater detail the effect of products offering nanoparticles for application in plant species of agricultural interest. The objective of this study was to determine the response of stevia ( Stevia rebaudiana B.) in vitro to different concentrations of AgNPs (silver nanoparticles), as well as to characterize and identify their absorption, translocation and accumulation mechanisms. Nodal segments of stevia grown in MS medium supplemented with AgNPs (0,12.5, 25, 50,100 and 200 mg L −1 ) were used. After 30 days of in vitro shoot proliferation, the number of shoots per explant, shoot length, chlorophyll content, dry matter content and the metallic silver (Ag) content of the plants were quantified. In addition, characterization, transport and accumulation of silver nanoparticles were performed by microscopic analysis. AgNPs were shown to be present in epidermal stem cells, within vascular bundles and in intermembrane spaces. In leaves, they were observed in ribs and stomata. The current and future use of AgNPs in agricultural sciences opens up the possibility of studying their effects on different plant species.

Salt stress limits productivity of crop plants, and differential responses may be observed among genotypes. Herein we analyzed the effects of saline stress induced by the application of different concentrations of sodium chloride (0.00, 0.25, 0.50, 0.75, and 1.00 M NaCl) in a local Mexican variety of purslane (Portulaca oleracea L.) named ‘Atlapulco’ in vegetative stage. The NaCl concentrations were applied in the Hoagland nutrient solution used in irrigation for 14 days under greenhouse conditions, using perlite as a substrate. Analysis of variance and comparison of means were carried out with the data obtained. NaCl concentrations from 0.50 M reduced canopy coverage 36.8% and stem diameter by almost 21%, while all NaCl doses reduced the leaf area by 28.2%, on average, as compared to the control. Dry stem biomass and chlorophyll b were reduced by the saline gradient. Secondary stems and root length increased with 1.00 M by 23 and 29%, respectively. Proline concentration both in leaves and stems increased by 223.9 and 138%, respectively, when applying 1.00 M NaCl, compared to the control. Applying 0.75 and 1.00 M NaCl reduced N concentrations by 47 and 28.8% in leaf tissues, respectively, compared to the control. The concentrations of P and K in leaves, and K in roots also decreased with the saline treatments, while those of Ca and Mg were not affected in any of the analyzed tissues. The highest concentrations of Na in leaves were observed in doses 0.50 and 0.75 M NaCl, surpassing the control by 67.5 and 73.1%, respectively. The findings reported herein are very useful to propose programs for the recovery of saline soils in the region and design environmental policies aimed at mitigating the effects of climate change on food production.

Salinity is one of the most critical factors affecting agriculture worldwide. The application of beneficial elements like silicon (Si) is one of the alternatives to mitigate its effects. In this research, we evaluated the effect of Si applied during seed imbibition on mitigating the negative effects caused by salinity during the germination and initial growth phases of maize (Zea mays L.) SB-308 seedlings. Seed pre-treatment during the imbibition was made with 0.0-, 1.5- and 3.0-mM Si. Afterwards, seeds that were imbibed were placed in plastic containers and treated with 0, 80, 160, and 240 mM NaCl. The evaluated concentrations of Si and NaCl gave rise to 12 treatments. Pre-treated seeds with 3 mM Si had an increase of weight after imbibition, 5.1% higher than the control. The treatments obtained from combining NaCl and Si levels did not affect the total and relative germination. The radicle length increased by 13.6% with 3 mM Si compared to the control. Conversely, it was lower with increasing salinity. These trends were observed in plant height. The interaction of the study factors produced an increase in the radicle length in the interval from 0 to 160 mM NaCl, when the Si dose was increased. However, there were no significant differences among equal levels of salinity without Si. It is concluded that Si increased the absorption of water during the imbibition and raised the index of velocity of germination under salinity, except in the dose 240 mM NaCl. Likewise, the pre-treatment of seeds with Si tends to increase radicle length under saline conditions.

Background Silver nanoparticles (AgNPs) display unique biological activities and may serve as novel biostimulators. Nonetheless, their biostimulant effects on germination, early growth, and major nutrient concentrations (N, P, and K) in tomato (Solanum lycopersicum) have been little explored. Methods Tomato seeds of the Vengador and Rio Grande cultivars were germinated on filter paper inside plastic containers in the presence of 0, 5, 10, and 20 mg/L AgNPs. Germination parameters were recorded daily, while early growth traits of seedlings were determined 20 days after applying the treatments (dat). To determine nutrient concentrations in leaves, a hydroponic experiment was established, adding AgNPs to the nutrient solution. Thirty-day-old plants were established in the hydroponic system and kept there for 7 days, and subsequently, leaves were harvested and nutrient concentrations were determined. Results The AgNPs applied did not affect germination parameters, whereas their application stimulated length and number of roots in a hormetic manner. In 37-day-old plants, low AgNP applications increased the concentrations of N, P, and K in leaves. Conclusion As novel biostimulants, AgNPs promoted root development, especially when applied at 5 mg/L. Furthermore, they increased N, P, and K concentration in leaves, which is advantageous for seedling performance during the early developmental stages.

We studied the effect of foliar applications (0, 0.4, 0.8, 1.2 and 1.6g-l-1) of boron on the concentrations of B, carbohydrates and total soluble amino acids in the leaf and on the thickness of the cell walls of buds in 2.5-year-old avocado cv. Hass trees. Penetration of foliar B application (0.8g4-1) occurred, but due to the natural fluorescence of the leaf, it was not possible to distinguish the path that the fertilizer followed, nor the time needed for absorption. The increasing levels of B applied in three successive occasions with 20 days intervals did not affect the concentration of this element in leaves, sampled 15 days after the application. There was no effect of B on the concentration of carbohydrates. After the second sampling, there was a positive relationship between the concentration of B applied and the amino acids concentration. Boron increased the cell wall thickness of the buds; 1.2 and 1.6gT1 doses increased cell wall thickness in the cortex by 66% and 84% respectively, while in the pith this increase was 71% and 77%, respectively, compared with the control. Based on the enhanced cell wall thickness observed, a concentration of B at 1.2g-l-1 is recommended for foliar application in avocado cv. Hass trees.

Lanthanum (La) is considered a beneficial element, capable of inducing hormesis. Hormesis is a dose-response relationship phenomenon characterized by low-dose stimulation and high-dose inhibition. Herein we tested the effect of 0 and 10 μM La on growth and biomolecule concentrations of seedlings of four sweet bell pepper ( L.) varieties, namely Sven, Sympathy, Yolo Wonder, and Zidenka. Seedling evaluations were performed 15 and 30 days after treatment applications (dat) under hydroponic greenhouse conditions. Seedling height was significantly increased by La, growing 20% taller in Yolo Wonder plants, in comparison to the control. Similarly, La significantly enhanced shoot diameter, with increases of 9 and 9.8% in measurements performed 15 and 30 dat, respectively, as compared to the control. Likewise, La-treated seedlings had a higher number of flower buds than the control. An increase in the number of leaves because of La application was observed in Yolo Wonder seedlings, both 15 and 30 dat, while leaf area was augmented in this variety only 30 dat. Nevertheless, La did not affect dry biomass accumulation. La effects on biomolecule concentration were differential over time. In all varieties, La stimulated the biosynthesis of chlorophyll and total 15 dat, though 30 dat only the varieties Sympathy and Yolo Wonder showed enhanced concentrations of these molecules because of La. Total soluble sugars increased in La-treated seedlings 30 dat. Interestingly, while most varieties exposed to La showed a reduction in amino acid concentration 15 dat, the opposite trend was observed 30 dat. Importantly, in all varieties evaluated, La stimulated soluble protein concentration 30 dat. It is important to note that while chlorophyll concentrations increased in all varieties exposed to La, both 15 and 30 dat, those of soluble sugars and proteins consistently increased only 30 dat, but not 15 dat. Our results confirm that La may improve seedling quality by enhancing some growth parameters and biomolecule concentrations, depending on the genotype, and time of exposure.

This research aimed to evaluate the effects of different concentrations of neodymium (Nd: 0, 2.885, 5.770, and 8.655 mg L−1, referred to as Nd0, Nd1, Nd2, and Nd3, respectively) and zinc (Zn: 0.1, 0.2, and 0.3 mg L−1, designated as Zn1, Zn2, and Zn3, respectively), as well as their combined interaction, on the nutritional content of lettuce (Lactuca sativa) cv. Ruby Sky. The seedlings were grown in a floating hydroponic system under greenhouse conditions. After 48 days of treatment, leaf samples were collected to determine their nutrient content. Leaf contents of N, P, Ca, Mg, S, Fe, Mn, B, and Nd were higher with the Nd1 (2.885 mg Nd L−1 + Zn1 (0.1 mg Zn L−1) treatment. The Nd3 (8.655 mg Nd L−1) + Zn3 (0.3 mg Zn L−1) treatment significantly increased the leaf contents of Cu and Zn. The K content was higher in leaves treated with Nd2 (5.770 mg Nd L−1) + Zn3 (0.3 mg Zn L−1). The joint application of Nd and Zn had positive effects on the nutrition of hydroponic lettuce, and Nd promoted the biofortification of lettuce by increasing leaf Zn content.

We evaluated the effects of neodymium (0.000, 2.885, 5.770 and 8.655 mg · L ) and zinc (0.1, 0.2 and 0.3 mg · L ), as well as their interaction on lettuce plants in hydroponics. Applications of 2.885 mg Nd · L and 5.770 mg Nd · L increased plant height, number of leaves and leaf area, as well as fresh and dry stem, root and total biomasses. Root volume was greater in plants treated with 2.885 mg Nd · L . With 0.1 mg Zn · L , plant height, leaf area and fresh stem, root and total biomass were greater, while applying 0.3 mg Zn · L increased the ratio of dry biomass of stems and roots. Plants exposed to 5.770 mg Nd · L + 0.3 mg Zn · L exhibited greater leaf length. The ratios of fresh and dry biomass of stems and roots increased in plants treated with 8.655 mg · L Nd + 0.3 mg Zn · L . Dry biomass weights of stems, roots and total were the highest in plants treated with 20 mg Nd · L + 0.1 mg Zn · L . Nd significantly increased foliar concentration of N, P and K. Hence, Nd and Zn improve growth and nutrition.

Nitrogen is a major plant macronutrient and its supply affects the entire metabolism of plants. This study evaluated the effect of different nitrogen concentrations in the nutrient solution: 0, 4.2, 8.4, and 12.6 mg L−1 Mexican marigold (Tagetes erecta L.) var. Inca plants in an open soilless culture system under greenhouse conditions on the concentration of chlorophylls, carotenoids, phenolics, and flavonoids derived from the secondary metabolism, as well as on the antioxidant activity in different tissues. With the 12.6 mg N L−1 dose, chlorophylls a, b, and total chlorophyll concentrations increased by 98.8, 11.9, and 56.6%, respectively. The highest concentrations of total carotenoids in flowers, 28–30%, were recorded in plants with doses of 8.4 mg N L−1. With doses of 12.6 mg N L−1, phenolic compounds and total flavonoids increased in leaves, but decreased in flowers. The low and medium N concentrations increased the antioxidant activity with respect to the control without N by 53% and 50.2%, respectively. We conclude that the applications of N in Tagetes erecta differentially affected the concentrations of photosynthetic pigments and biomolecules with antioxidant capacity, and that such effects were dependent on the doses of N tested and the plant organ evaluated.

Mexico is the main producer of avocado (Persea americana Mill.), contributing 31% of the world supply, which provides the country with an annual income of more than 2 billion dollars. The increase in national production is the result of a larger cultivated area, and not an increase in yields. In the State of Mexico, Mexico around 10 thousand hectares are cultivated with avocado trees, although 77% of the producers do not have specialized technical advice that offers reliable information on crop nutrition. This lack of advice and technical support detracts from volume and quality of production. The objective of this research was to carry out the nutritional diagnosis of an avocado orchard in Tejupilco, State of Mexico, Mexico, through the Compositional Nutrient Diagnosis (CND), and to generate specific fertilization recommendations for the study area, for which leaf and soil analyses were carried out. Each nutrient determined in the leaf analysis (N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, and B) was compared with its optimal concentration according to literature. The CND yielded relative deficiency or excess indices that determined the order of nutritional limitation. Zn, B, S, and K deficiencies were detected in all sampled areas, while P, Mn, and Cu were deficient only in some areas. N, Ca, Mg, and Fe did not show nutritional limitation. Recommendations were formulated to address each of the nutritional deficiencies and the problem of sodicity revealed by the soil analysis. This is the first work in which the CND is used to assess the nutritional situation of avocado orchards in the world.