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.

The objective of this work was to evaluate the influence of shade level on the production of T. myrmecophila seedlings. After 30 days of seedling transplantation, the seedlings were submitted to the following treatments: 100% light (full sun), 75% light and 50% light. The statistical design was completely randomized with 5 replicates of 10 seedlings each per treatment. The data were analyzed by repeated measures in time, in 5 measurements, performed every 30 days (150 days of evaluation). The analyzed variables were shoot height and diameter. The environment with 75% luminosity was the one that contributed most to the growth in height of the seedlings, having presented higher mean values over time, in the 5th month (34.94 cm). The most pronounced effect for growth in diameter was verified in the 5th month of evaluation, where the highest average was obtained in the environment with 50% of shading (4.61 mm). The T. myrmecophila seedlings were influenced by the shading levels used. From the results evaluated, treatments with 75% and 50% of solar radiation provided superior growth for dendrometric variables height and diameter, respectively. Therefore, we recommend environments with 75% and 50% of solar radiation for the production of T. Myrmecophila seedlings.

RESUMOFatores abióticos como a deficiência hídrica e a salinidade reduzem a produção do sorgo. Durante a fase germinativa e de estabelecimento da plântula não é diferente, uma vez que a embebição é fundamental em todos os processos fisiológicos e no transporte de substâncias indispensáveis para seu crescimento e desenvolvimento. Mediante a isso, o objetivo do trabalho foi avaliar o efeito do estresse salino e hídrico na germinação de sementes de sorgo, avaliando o comportamento germinativo (porcentagem de germinação, índice de velocidade, tempo médio e a primeira contagem de germinação). O trabalho foi desenvolvido na Universidade Federal Rural da Amazônia (UFRA -Campus Belém), utilizando sementes de sorgo [Sorghum bicolor (L) Moench] cultivar BRS 310. O experimento foi dividido em dois delineamentos inteiramente casualizados separados para cada estresse (hídrico e salino). O primeiro composto por 5 concentrações de NaCl (0,0; 50; 100; 150 e 200 mmol) e o segundo composto por 4 tratamentos (0,0; -0,3; -0,6; -0,9 MPa), no qual as soluções de Polietilenoglicol 6000 simularam tais potenciais osmóticos. A germinação de sementes de sorgo foi comprometida pelo aumento das concentrações de NaCl, assim como a redução dos potenciais osmóticos simulados de PEG-6000.Palavras-chave: germinação, déficit hídrico, salinidade, sorghum bicolor. ABSTRACTAbiotic factors such as water deficiency and salinity reduce sorghum production. It is no different during the germination and seedling establishment phase, as imbibition is fundamental in all physiological processes and in the transport of substances essential for its growth and development. Therefore, the objective of this work was to evaluate the effect of saline and water stress on sorghum seed germination, evaluating germination behavior (germination percentage, speed index, average time and first germination count). The work was developed at Federal Rural University of Amazônia (UFRA -Belém Campus), utilizing sorghum seeds [Sorghum bicolor (L) Moench] BRS 310 cultivar. The experiment was divided into two completely randomized designs for each stress (water and saline). The first compound comprises 5 NaCl concentrations (0.0; 50; 100; 150 and 200 mmol) and the second compound comprises 4 treatments (0.0; -0.3; -0.6; -0.9 MPa), in which Polyethylene glycol 6000 solutions simulated such osmotic potentials. Sorghum seed germination was compromised by increased NaCl concentrations as well as reduced simulated PEG-6000 osmotic potentials.