Glutathione, a peptide frequently associated with the antioxidant mechanism of plants against reactive oxygen species, and proline, an amino acid whose function is related to cellular homeostasis, can both contribute to improve plant tolerance under situations of abiotic stress, such as boron toxicity. Aims of this research were to (i) quantify the oxidant and antioxidant compounds, (ii) evaluate the photosynthetic pigments, (iii) determine amino acids and PRO, and (iv) determine whether GSH and PRO contribute to the tolerance mechanisms in young Schizolobium parahyba var. amazonicum plants under B toxicity. This experiment tested five boron levels (25, 50, 100, 150 and 250 µM B), being evaluated physiological and biochemical variables. The values reported to proline levels presented significant variation for treatments with 50, 100, 150 and 250 µM B, with increases for the 150 and 250 µM B levels, being 45.2 and 52.4%, respectively. This study found that boron toxicity promoted similar behaviours in both the leaves and root, which included progressive increases in hydrogen peroxide, electrolyte leakage, amino acids and proline, and decreases in total glutathione, chlorophyll a, chlorophyll b and total chlorophyll, confirming that proline but not glutathione actively participates in the tolerance mechanism of young Schizolobium parahyba plants exposed to boron toxicity.

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Soybean is a legume widely cultivated globally for its seeds, which are rich in oil and protein suitable for animal and human nutrition, and as a biofuel source. One of the main factors that limits production is soil salinity; currently there are an estimated 800 million hectares of agricultural land affected by salt stress worldwide. The aim of this research was to determine whether anatomical, morphological, nutritional, physiological, and biochemical parameters are negatively affected in soybean plants cultivated under different levels of salt stress. The experiment was randomized into five treatments (0, 50, 100, 150, and 200 mM Na+). Plants subjected to concentrations of 50 to 200 mM Na+ exhibited reductions in K (range 21% to 57%), Ca (range 38% to 63%), and Mg (range 20% to 41%) compared to controls (without Na+). Na+ stress progressively produced negative effects on photosynthetic machinery, gas exchange, and photosynthetic pigments, results clearly related to oxidative stress generated by the saline growth conditions. Interestingly, our study revealed that at concentrations up to 100 mM Na+ deposition of epicuticular wax occurred, the quantity and shape of the stomata changed, and the thickness of the leaf epidermis increased. Our broad-based, multidisciplinary, and comparative study proved that soybean plants suffer significant deleterious effects modulated by Na+ stress, mainly at concentrations above 100 mM Na+.

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Boron (B) supply has been studied as an alternative to alleviate environmental stress conditions in forest essences due to the functions that B plays within the plant cell in the metabolism of compounds and polysaccharides connection. Thus, it was postulated the hypothesis that B may provide greater resistance from Paricá (Schizolobium parahyba) to water deficit. The aim was to evaluate growth parameters, photosynthetic rate, nutritional efficiencies, and B content of young Schizolobium parahyba plants as a function of the factors B levels and water deficit. Experiment was a completely randomized factorial, with two B concentrations (25 and 250 μmol L-1 , simulating sufficient and high B conditions, respectively) and two water conditions (deficit and no deficit). Factors analyzed influenced growth, accumulation, photosynthetic and nutritional efficiency variables. There was an increase in the growth of stem, root and in the Dickson quality index of plants of Paricá with high concentration of B, when they were under water deficit. Concentration and accumulation of B was higher in plants under water deficit with high concentration of B, as well as the efficiency of absorption and translocation, indicating that high B nutrition attenuates the effect of water deficit in young plants in Paricá.

Boron (B) is a very important nutrient required by forest plants; when supplied in adequate amounts, plants can ameliorate the negative effects of abiotic stresses. The objective of this study was to (i) investigate gas exchange, (ii) measure oxidant and antioxidant compounds, and (iii) respond how B supply acts on tolerance mechanism to water deficit in young Schizolobium parahyba plants. The experiment employed a factorial that was entirely randomised, with two boron levels (25 and 250 µmol L -1 , simulating conditions of sufficient B and high B, respectively) and two water conditions (control and water deficit). Water deficit induced negative modifications on net photosynthetic rate, stomatal conductance and water use efficiency, while B high promoted intensification of the effects on stomatal conductance and water use efficiency. Hydrogen peroxide and electrolyte leakage of both tissues suffered non-significant increases after B high and when applied water deficit. Ascorbate levels presented increases after water deficit and B high to leaf and root. Our results suggested that the tolerance mechanism to water deficit in young Schizolobium parahyba plants is coupled to increases in total glutathione and ascorbate aiming to control the overproduction of hydrogen peroxide and alleviates the negative consequences on electrolyte leakage and gas exchange. In relation to B supply, this study proved that sufficient level promoted better responses under control and water deficit conditions.

The tropical Amazon has a unique biodiversity that has been affected by the development of pastures and economically important crops, such as soybeans. In the Amazon soil, the communities of microorganisms are diverse and act in different biogeochemical activities relevant to their adaptation to the environment. The assessment of changes in soil microorganism communities is essential to consider the impact of agribusiness action in one of the wealthiest regions in diversity in the world. Thus, the soil microbial diversity of the Amazon forest, the north region of Brazil, was evaluated regarding the influence of soybean farming with regions with periods of two and 14 years of exploitation, with regions of pasture and forest area, through the metagenomics approach with new generation sequencing technology, in addition, it was considered chemical characteristics such as pH value, organic matter content, macronutrients, micronutrients, and cations. High microbial diversity was identified at all collection sites and, despite this, bacterial, archaeal, and virus communities were very diverse between sites, with higher identification of Enterobacter cloacae and species of Pseudomonas, Pseudoplusia includens, Methanosarcina barkeri in the farmed and pasture, whose microbial diversity is influenced by the presence of cations and the interaction of organic matter with clay. It was evident that there is a change in the communities of native microorganisms for others adapted in the areas that had their vegetal cover eliminated.

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