Luma Castro de Souza

This research was carried out with the aim of evaluating the attenuating effect of 24-epibrassinolide (EBL) on oxidative stress at emergence in paricá seedlings subjected to arsenic (As) toxicity. Paricá seeds (Schizolobium amazonicum Huber ex Ducke) were used in an experiment with a completely randomized experimental design (DIC) with factorial combinations between three concentrations of 24- epibrassinolide (0, 10 nM and 20nM) and four concentrations of sodium arsenite (NaAsO2 - 0.2 mg L-1, 4 mg L-1, 6 mg L-1). The EBL positively influenced the emergence percentage and shoot and root growth, mainly in the dosage of 20nM of EBL. However, the increase in arsenic concentration had a negative effect on these parameters, mainly at a dosage of 6 mg. L-1. Analysis of the antioxidant system showed that the level of SOD (Superoxide Dismutase) remained constant, the production of APX (Ascorbate Peroxidase) and G-POD (Guaiacol Peroxidase) is negatively modulated by EBL in the leaves. In the root, APX showed low levels and the concentration of G-POD increased with dosages of 20nM of EBL. In summary, doses of 20nM of EBL showed evidence of an attenuating effect on the percentage of emergence, shoot growth and stimulation of G-POD activity.

Although silicon is not considered an essential element, in some crops such as soybeans, its supply can stimulate plant development and plant production. The growth of soybean cultivars in Cerrado soil subjected to the application of silicon doses was studied. The experiment was conducted in a greenhouse at the Instituto Federal do Amapá – IFAP/Campus Agrícola Porto Grande. The experimental design was completely randomized, arranged in a 5x2 factorial scheme, with four replications. The factors consisted of the control treatment (without Si) and four doses of Si (250, 500, 750 and 1000 mg pot^-1 of SiO₂), and two soybean cultivars (BRS Tracajá and FTS Paragominas). Growth variables were analyzed, such as: plant height, stem diameter; and dry matter of shoots and roots. Silicon influenced the increase in height when evaluating the cultivars and isolated doses, the same behavior was observed in the dry matter production of the aerial part and total. The element silicon helps in the improvement and gain in height and other evaluated agronomic characteristics, but studies with this element must be more applied, to obtain the answer for other variables and study conditions.

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 aim of this work was applying salicylic acid (SA) in cowpea seedlings under saline stress. The experiment took place in the seed laboratory of the Universidade Federal Rural da Amazônia with a completely randomized experimental design in a 2 x 2 x 3 factorial scheme, with two bean cultivars (Canapu and Pingo-de-ouro), two levels of salicylic acid (0, and 0.50 mM) and three salt stress levels (0, 25, 50 mM). The seeds were previously soaked in salicylic acid (0 and 0.50 mM) for a period of 12 hours and then placed in germitest paper rolls for treatments with NaCl (0, 25, 50 mM) for a period of 12 days at room temperature constant 27 °C. There was a significant effect of cultivars, AS dose and NaCl concentrations and their interactions on most of the analyzed variables. Root and leaf proline concentrations were higher in pingo-de-ouro cultivar, Canapu cultivar had better performance in biomass accumulation. Salicylic acid reduced proteins in the leaves by 13.33%, while in the root there was an increase of 12.61%, ammonium concentrations reduced in the roots by 11.9%. When applied to salinity (25 and 50 mM) there was an increase of proteins in the leaves 40.83% and 27.48% respectively, and a reduction of amino acids of 30.24 and 25.24% in NaCl dosages (25 and 50 mM) respectively. Salinity reduced biomass accumulation and interfered with cellular solute production. However, the application of salicylic acid promoted salt stress tolerance in Canapu cultivar.

The cowpea bean [Vigna unguiculata (L.) Walp.], a legume of great socioeconomic importance, it was previously cultivated exclusively for subsistence and commercial purposes, especially in the North and Northeast regions. This crop has a low production cost and high nutritional value, in addition to a high potential for productivity growth and expansion to other regions. The objective of this work was to evaluate parameters of growth and production in cowpea culture, as a function of potassium fertilization in soil of the cerrado of Amapá. The parameters of growth and production of the cowpea culture were evaluated, as a function of potassium fertilization in the soil of the cerrado of Amapá. The experiment was conducted in a greenhouse, using a completely randomized experimental design, with four replications, in a 5x2 factorial scheme, totaling 40 experimental units, which were composed of plastic pots containing 7 dm³ of soil collected from the arable layer (0-20 cm ) of a typical Hyperdystrophic Yellow Argisol, with a sandy clay loam texture, in a cerrado area in the municipality of Porto Grande-AP. The factors consisted of the control treatment (without K), four doses of K (45, 90, 135 and 180 kg ha^-1) in the form of potassium chloride, and two cowpea cultivars (Pretinho and BRS Tumucumaque). The cultivar BRS Tumucumaque shows better growth and production of cowpea plants. Doses of 90 kg ha^-1 provided greater height (98.75 cm) and stem diameter (10.0 mm). As for production, the dose of 135 kg ha^-1 caused greater grain weight gain (5.25 g) and dry mass of pods (13.92 g), and the doses of 90 and 180 kg ha^-1 induced greater number and length of pods (3.16 pods) respectively. These results show better responsiveness of the BRS Tumucumaque cultivar at doses of 90, 135 and 180 kg ha^-1 in the type of soil where the study was conducted.

The water deficit in particular, reduces the productivity of vegetable crops. To minimize these harmful effects on agriculture, several agronomic and physiological practices are being studied, such as the use of bacteria and water stress attenuators, such as brassinosteroids. Considering the socioeconomic relevance of corn culture and its sensitivity when exposed to water deficit, the objective of the present study was to evaluate the action of brassinosteroids and azospirillum on nitrogen metabolism in corn plants subjected to water stress conditions. The experiment was carried out in a greenhouse, in a period of 47 days, with corn plants, using the hybrid K9606 VIP3. The design was completely randomized, in a 2x2x3 factorial scheme, with six replications. The first factor corresponds to two water regimes (presence and absence of water deficit). The second corresponds to inoculation via seed of Azospirillum brasiliense and absence of inoculation. And the third corresponds to the application of three concentrations of brassinosteroids (0, 0.3 and 0.6 μM). Were determined Nitrate; nitrate reductase; free ammonium; total soluble aminoacids; soluble proteins; proline; glycine betaine and glutamine synthetase. The lack of water in plants provided a reduction in the protein and nitrate reductase contents, in leaves and roots. For ammonium, plants with water deficit inoculated at a concentration of 0.3 μM, obtained an increase of 7.16 (70.26%) and 13.89 (77.04%) mmol NH₄ ⁺ .Kg^-1. DM (Dry mass) on the leaf and root respectively. The water deficit in the soil provided significant increases in the concentrations of glycine betaine, nitrate, proline and aminoacids, both in the leaves and in the roots of the corn plants. On the other hand, the contents of glutamine synthetase had a reduction in both leaves and roots.

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.

Espécimes de Pectis elongata Kunth apresentam variações de aromas quando maceradas, alguns acessos apresentam aroma de cominho(PCH), enquanto outros apresentam aroma de capim-santo(PCS). O objetivo deste trabalho foi avaliar as variações morfoanatômicas dentre esses espécimes e caracterizá-los nesses aspectos. A partir de material fértil com mesmo nível de desenvolvimento, foram feitos registros morfológicos com desenhos à Nankin, seguindo as técnicas usuais na composição de pranchas para fins taxonômicos. As fotomicrografias em microscopia fotônica foram obtidas a partir de lâminas histológicas dos órgãos vegetativos caule e folha, confeccionadas a mão livre, seguindo as técnicas usuais da anatomia vegetal. Os espécimes PCH apresentaram estrutura caulinar com seis lados bem destacados, entrenós mais alongados e com poucas ramificações; folhas mais desenvolvidas e com menor quantidade de emergências na margem; nó com menor quantidade de estípulas quando comparados com amostra de PCS, cujo caule apresentam entrenós mais curtos, amplamente ramificado; folhas menores com até quatro emergências na base foliar e nó com quatro estípulas. As folhas são anfiestomáticas, com estômatos anisocíticos em ambos espécimes, mesofilo dorsiventral e presença de bainha Kranz contornando os feixes vasculares e cavidades secretoras são mais destacadas nos espécimes PCS. A caracterização em nível morfológico e anatômico ratificam outras publicações no gênero Pectis. As variações morfoanatômicas são perceptíveis, entretanto não são suficientemente diagnósticas para afirmarmos tratar-se de espécies diferentes, mas há forte indício de constituírem diferentes quimiotipos.

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.