O referido experimento foi desenvolvido com o objetivo de avaliar os efeitos de diferentes dosagens de silício via aplicação foliar em plantas de híbridos de Tomate submetidos a estresse hídrico, em condições de cultivo protegido. Utilizou-se o delineamento experimental inteiramente casualizado, com uma testemunha e cinco concentrações de silicato de potássio (0, 25, 50, 75 e 100 ml.L-1 de K2SiO3), e 10 repetições cada. As avaliações ocorreram aos 20, 35, 50, 65 e 80 DAT para: altura das plantas; diâmetro do caule; número de folhas e porcentagem de clorofila e aos 27, 39, 51, 63, 75 e 87 DAT: número de flores e número de cachos. Também foram avaliados comprimento e peso seco do sistema radicular, número total de frutos por planta, peso total de frutos, diâmetros longitudinal e vertical dos frutos. Os resultados obtidos foram submetidos à análise de variância e de regressão polinomial. A adubação com silicato de potássio nas concentrações de 25 e 50 ml.L-1 apresentaram efeito positivo para as variáveis analisadas, assim, sendo indicadas sua aplicação em plantas de tomate por minimizarem os efeitos do déficit hídrico.

O referido experimento foi desenvolvido com o objetivo de avaliar os efeitos de diferentes dosagens de silício via aplicação foliar em plantas de híbridos de Tomate irrigadas com água salina, em condições de cultivo protegido. Utilizou-se o delineamento experimental inteiramente casualizado, com uma testemunha e cinco concentrações de silicato de potássio (K2SiO3), e 10 repetições cada. As avaliações ocorreram aos 20, 45, 75 e 90 DAT para: alturas de plantas; diâmetro do caule; número de folhas e porcentagem de clorofila e aos 27, 47, 79 e 87 DAT: número de flores e número de cachos. Também foram avaliados comprimento, volume e peso seco do sistema radicular, número total de frutos por planta, peso total de frutos, diâmetros longitudinal e vertical dos frutos. Os resultados obtidos foram submetidos à análise de variância (F ≤ 0,05), e as médias submetidas ao teste de Tukey (P ≤ 0,05) e análise de regressão polinomial. Para as variáveis altura da planta, volume, peso fresco, peso seco das raízes, a melhor dosagem foi a de 25 ml.L-1 de K2SiO3, enquanto que a dosagem de 75 ml.L-1 de K2SiO3 proporcionou melhores resultados para matéria seca das raízes, número de folhas e de flores.

Salinity is prejudicial to plant development, causing different types of damage to species, or even between genotypes of the same species, with the effects being aggravated when combined with other types of stress, such as heat stress. The aim of this study was to evaluate the tolerance of cowpea genotypes (Vigna unguiculata L. Walp.) to salt stress at different temperatures. Seeds of the Pujante, Epace 10 and Marataoã genotypes were placed on paper rolls (Germitest®) moistened with different salt concentrations of 0.0 (control), 1.5, 3.0, 4.5 and 6.0 dS m-1, and placed in a germination chamber (BOD) at temperatures of 20, 25, 30 and 35°C. The experiment was conducted in a completely randomised design, in a 3 × 4 × 5 scheme of subdivided plots, with four replications per treatment. The variables under analysis were germination percentage, first germination count, shoot and root length, and total seedling dry weight. At temperatures of 30 and 35°C, increases in the salt concentration were more damaging to germination in the Epace 10 and Pujante genotypes, while for the Marataoã genotype, damage occurred at the temperature of 20°C. At 25°C, germination and vigour in the genotypes were higher, with the Pujante genotype proving to be more tolerant to salt stress, whereas Epace 10 and Marataoã were more tolerant to high temperatures. Germination in the cowpea genotypes was more sensitive to salt stress when subjected to heat stress caused by the low temperature of 20°C or high temperature of 35°C.

Salinity adversely affects plant growth and metabolism by triggering increased production of reactive oxygen species (ROS). Ascorbic acid (AsA) is known to protect organelles and cells against ROS by preventing accumulation. The objective of this study was to study the effects of AsA on cowpea beans under saline stress. Cowpea seeds of the cultivars (BRS Marataoã and Setentão) were conditioned at concentrations of 0.0 (control); 0.25; 0.50; 0.75 and 1.00 mM AsA and seeded on paper towels, moistened at saline levels of 0.0 (control); 1.5; 3.0; 4.5; 6.0 and 7.5 dS.m-1, packed in a bench germinator at 25 °C. The statistical design adopted was a completely randomized 2 × 5 × 6 factorial design (cultivar x ascorbic acid x saline levels) with four replicates of 50 seeds per treatment. The analyzed variables were percentage of germination, first germination count, germination speed index, shoot and root length, total seedling dry weight, and leaf and root electrolyte leakage. Ascorbic acid at concentrations of 0.50 mM for BRS Marataoã and 0.75 mM for the Setentão, enabled the development of more vigorous seedlings and the reduction of membrane damage caused by oxidative stress both in the absence of salt and at the saline levels tested, including the highest one.

Salinity and water deficiency are abiotic factors which have a strong impact on agricultural activities, especially in arid and semi-arid regions. The aim of this research was to analyse the tolerance of two genotypes of forage sorghum, EA 116 and BRS Ponta Negra, to different levels of water and salt stress during germination. The conditions of water and salt stress were simulated by moistening the substrate with a solution of mannitol and of sodium chloride (NaCl) respectively, with the water potential adjusted to 0 (distilled water), -0.1, -0.2, -0.3, -0.4, -0.5 and -0.6 MPa. The variables under analysis were germination percentage, first count, germination speed index, shoot and root length, seedling dry weight, electrolyte leakage and leaf Na+/K+ ratio. The experiment was conducted in a completely randomised design, and distributed in a 2 (genotypes) × 2 (stress condition) × 7 (osmotic potential) factorial scheme, with four replications. The EA 116 and BRS Ponta Negra genotypes show greater tolerance to water stress. The EA 116 cultivar maintained germination under water stress from 0 to -0.6 MPa and saline stress from 0 to -0.4 MPa.