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 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.