The objective of the present research was to study nitrogen metabolism in sorghum plants subjected to salt stress and silicon concentration. The experiment was conducted at the Amazon Federal Rural University, Capitão Poço Decentralized Unit for 1 month, in 2013, using the cultivar BR 700 of forage sorghum plants (Sorghum bicolor [Moench.]). The experimental design was completely randomized, in a 5 × 3 factorial arrangement (0, 50, 100, 150 and 200 µM of silicon) and saline concentrations (0, 1.5 and 2.0 M), consisting of 4 replications. Analyses were conducted of amino acids, proteins, free ammonium, nitrate and nitrate reductase. Nitrate content increased in the leaves and root in the treatments 0 and 1.5 µM of Si, but decreased in treatments with the 0.5 and 1.0 µM doses of Si. In leaves and roots, the treatments 1.5 and 2.0 of SC caused reduction and increase, respectively, of ammonium levels. The silicon doses attenuated the negative effects of the treatments on the biochemical compounds caused by higher salt concentrations in sorghum plants.

The Parkia gigantocarpa is a neotropical tree that naturally occurs in terra firme forest and floodplain. The aim of the study was to evaluate the physiological and biochemical behavior in young plants of P. gigantocarpa subjected to waterlogging conditions. The waterlogging was imposed at approximately 5 cm above the blade surface of the soil using pots with a capacity of 14 kg of substrate. The experimental design was completely randomized with two water conditions (control and waterlogging) combined with five evaluation times (0, 4, 8, 12 and 16-days waterlogging conditions). The variables evaluated were: Predawn water potential ( p Ψ); the foliar xylem water potential ( x Ψ); hydraulic conductivity; concentration of nitrate; nitrate-reductase activity (NRA); glutamine-synthetase (GS); total soluble amino acids; proline; glycine-betaine; alcohol-dehydrogenase (ADH) and lactatedehydrogenase activity (LDH). The significant reduction in x Ψ and hydraulic conductivity continued until the 8th day in plants subjected to waterlogging, with subsequent stabilization. The concentration of nitrate, NRA, GS, and total soluble amino acids reduced significantly, in the leaves of plants subjected to waterlogging. The waterlogging increased the proline and glycine-betaine, mainly, in the leaves. The ADH activity was significantly higher in the root of the flooded plants, especially, on the 16th day of flooding. In the same period, the LDH activity showed the highest values, mainly, in the leaves of flooded plants. The results showed susceptibility of young plants of P. gigantocarpa subject to waterlogging conditions.

The objective of the present work was to verify, through multivariate analysis, the behavior patterns of biochemical compounds in forage sorghum, submitted to different silicon applications and water stress. Experiment with forage sorghum (Sorghum bicolor L. Moench), variety BR 700, was conducted in a greenhouse. The experimental design was completely randomized in a 2×4 factorial arrangement with seven replicates, two hydric conditions (irrigated and water deficit) and four silicon applications (0.5, 1.0, 1.5 and 2.0 M). The multivariate analysis showed that when there is no shortage of water and regardless of the silicon dose, nitrate levels were higher and carbohydrate, proline and sucrose levels were lower in leaves and roots. The quantity of biochemical compounds differed between sorghum leaves and roots. This condition also varied according to the soil water stress. Silicon application in sorghum plants mitigates the negative effect of drought stress, favoring this crop cultivation in areas of low water availability. Nonetheless, differences between silicon doses were not observed in this experiment. Therefore, it is recommended that this chemical should be applied in drought-ridden areas.

The hog plum tree is a species exploited extractively, but this information is not included in official statistics, despite the socioeconomic relevance of the species in the North and Northeast of Brazil. The present study aimed to analyze physiological and biochemical processes in Spondia mombin L. plants under two water regimes. The experiment was conducted in a greenhouse at the Federal Rural University of the Amazon, Belém, PA. The experimental design was completely randomized with two water conditions: control and water deficit, with 20 repetitions totaling 40 experimental units, where each experimental unit consisted of one (1) plant/pot. Moderate/severe water deficit was simulated by suspending irrigation of the seedlings, respectively, for a 15-day period. There were reductions in the levels of water potential, nitrate, nitrate reductase and proteins, while the values for ammonium, glutamine synthetase, amino acids, proline and glycine betaine had a significant increase in plants under water stress compared with control plants. Young hog plum plants under water deficit undergo changes in nitrogen metabolic pathways. These changes are indicative of intolerance to extremely dry environments.