Water stress limits the initial growth and development of maize mass and grain, as well as the physiological process for absorbing the amount of mineral elements. The objective was to evaluate the effect of silicon on germination and growth of corn seedlings submitted to water deficit. The experiment was carried out in the laboratory and the experimental design was completely randomized (factorial 3 × 4), with three concentrations of calcium silicate (0.0; 1.0 and 2.0 mM) and 4 solutions of PEG-6000 to simulate different osmotic potentials (0, 0; -0.3; -0.6; -0.9 MPa). Germination percentage, germination speed index (GSI), mean germination time (MGT), percentage of non-germinated and abnormal germinated, length and dry matter of shoot, root and total seedlings were evaluated. Water deficiency reduced the parameters TG, GSI and MGT. The water deficit reduce the MSPA, MSR and MST with more than 80% reduction in mass from seedlings without deficiency to seedlings with deficiency. For CPA, CR and CT there was a reduction of at least 87%, 70% and 77%, respectively, among seeds without deficiency compared to seeds submitted to deficiency. The use of silicon in corn seeds did not attenuate the stress caused by water deficit simulated by PEG-6000.

Cowpea (Vigna unguiculata (L.) Walp.) is a legume widely cultivated by small, medium and large producers in several Brazilian regions. However, one of the concerns for the production of cowpea in Brazil in recent years is the low rainfall activity in these regions, which generates the accumulation of salts on the surface. The objective of this work was to evaluate the effects of salt stress on growth parameters and enzyme activity in cowpea plants at different concentrations of brassinosteroids. Experiment was developed in a greenhouse using a completely randomized experimental design in a 3 x 3 factorial scheme. The treatments consisted of three levels of brassinosteroids (0, 3 and 6 µM EBL) and three levels of salt stress (0, 50 and 100 mM NaCl). Growth factors (height, diameter and number of leaves) decreased in the saline condition. With the presence of brassinosteroid the height did not increase, but the number of leaves did, mainly in the saline dosage of 100 mM NaCl. In the variable membrane integrity, brassinosteroid was efficient in both salinity dosages, the same not happening with the relative water content, where the saline condition did not affect the amount of water in the vegetable, with the application of brassino it remained high, decreasing only at dosage 100 mM NaCl. The nitrate reductase enzyme was greatly affected in the root system even with the application of increasing doses of brassino. Therefore, brassinosteroids as a promoter of saline tolerance in cowpea seedlings was positive. The concentration of 3µM of EBL provided the most satisfactory effect in tolerating the deleterious effects of the saline condition. The same cannot be concluded for the concentration of 6µM of EBL that did not promote tolerance to some variables.

As an essential element, Nitrogen is needed in large quantities for being an important component of cellular constituents and for plant metabolism, and its deficiency is one of the most common limitations for plant development. The study of the toxic effects of metal in plants involves a complex system of reactions that can be better determined once having a large attention of the different backgrounds of occurence to determinate how to proceed. The objective of this review is to add scientific knowledge, addressing the main functionalities and characteristics of this relation heavy metals – nitrogen metabolism in plant. Increasing industrialization and urbanization had anthropogenic contribution of heavy metals in biosphere and had largest availability in ecosystems. This toxicity in plants varies with plant species, specific metal, concentration, soil composition, as many heavy metals are considered to be essential for plant growth. Were provided data and reviews regarding the effect of heavy metals on nitrogen metabolism of plants and the responses of plants and the cross-talk of heavy metals and various stressors factors. Is clear to understand the relation between metals amount and the benefit or harm caused on plants, determining then, which mechanism should be activated to protect your physiological system.

Cowpea is a leguminous plant belonging to the fabaceae family cultivated in the North and Northeast regions of Brazil, with productive potential. Among the abiotic factors, water deficiency is one of the main environmental limitations that influence agricultural production in the world. The objective of this work was to study the relative water content and osmoregulators of cowpea plants subjected to water stress. The experiment was carried out in a greenhouse at the Universidade Federal Rural da Amazônia (UFRA, Belém, PA), cowpea plants BR-17 Gurguéia Vigna unguiculata (L.) Walp were used. The experimental design was completely randomized (DIC) in a 2 × 2 factorial scheme, two water conditions (control and water deficit) and two times of stress (four and six days of water suspension), with 7 replications, totaling 28 experimental units. The water deficit affected plants, causing a reduction in relative water content (69.98%), starch (12.84% in leaves and 23.48% in roots) and carbohydrates (84.34%), and an increase in glycine-betaine, sucrose (114.11% in leaves and 18.71% in roots) and proline (358.86%) at time 2. The relative water content was negatively affected by water conditions, with a decrease in relation to the interaction of the aerial part and the root system. Therefore, greater metabolic responses were noted in plants that were subjected to stress treatment at time 2 (6 days).

The development of anthropogenic activities such as industry, mining, agriculture, urban waste discard has been, the main actions that result in increased contamination by heavy metals in soil, water and air. One of the most harmful metals made available by these activities is cadmium, and even at low concentrations it is very toxic mainly in plant structures. The objective of this work was to verify the biochemical behavior of nitrogen and carbon metabolism in young plants of paricá when submitted to increasing cadmium application. For this, a completely randomized experiment was carried out with five treatments (control, CdCl2 178 μM, CdCl2 356 μM, CdCl2 534 μM, CdCl2 712 μM), with seven replicates, totaling 35 experimental units. The sensitivity of this vegetable to the increasing concentrations of cadmium was evident. The root system it presents’’ saw where the most toxic element accumulated, solutes such as carbohydrates, sucrose were affected in their concentrations, mainly in the leaves. The root system saw in its concentrations of glycine betaine a possibility of osmoprotection, but this did not reflect an increase in the concentration of nitrate in both leaf and roots. In the other hand, this fact not observed by the concentration of ammonium that increased in the root system. The results showed that the cadmium was transported to aerial part, however, concentrated mainly in the root system characterizing as a phytoextractor species.

O mogno africano (Khaya grandifoliola) é uma espécie arbórea que vem ganhando espaço no mercado florestal, apresentando utilidade nas mais diversas utilizações, principalmente em território brasileiro, onde é o principal substituto da madeira do mogno brasileiro. O objetivo deste trabalho foi realizar uma análise de trilha entre a resposta da solução nutritiva ao tratamento com cádmio e as demais variáveis e atributos estudados: aminoácido, nitrato, proteína, amônio, redutase, IDM, cádmio. O experimento foi conduzido em casa de vegetação. A princípio, as mudas foram habituadas para posteriormente serem levadas ao tratamento, onde a aplicabilidade se deu pelo cloreto de cádmio monohidratado (CdCl 2.H2O) de acordo com a solução nutritiva. O delineamento experimental foi inteiramente casualizado (DIC), misturado em cinco concentrações (0; 10; 20; 30 e 40 mg L-1) com sete repetições, totalizando 35 unidades experimentais. Para realizar o exame comparativo, os dados foram submetidos à análise de variância, seguida de análise de regressão. A análise de trilha permitiu verificar diretamente que doses crescentes de tratamento com Cádmio (CAR) refletiram em correlação negativa com o teor de aminoácidos (TAA) nas raízes das plantas de mogno. O estresse abiótico, que foi a exposição a um produto químico tóxico (cádmio), diminuiu, neste caso, a capacidade das plantas de sintetizar aminoácidos. O aumento das doses de tratamento com cádmio (CAL) refletiu em correlação negativa com o teor de proteína na folha (PRL) das plantas de mogno. Evidentemente, quanto maior a concentração de cádmio, maiores serão os danos aos sistemas metabólicos do mogno. Com este estudo, evidenciamos que excesso de cádmio no solo afeta o desenvolvimento de mudas de espécies florestais como o mogno.