RESUMO

Cowpea is the main subsistence crop-protein source-for the Brazilian semi-arid region. The use of salt-stress-tolerant varieties can improve crop yields. We evaluated the effect of irrigation with brackish water on the growth, photosynthetic responses, production, and tolerance of fifteen traditional varieties of cowpea. The experiment was conducted in randomized blocks, in a 15 × 2 factorial scheme, composed of 15 traditional varieties of cowpea and two salinity levels of irrigation water (0.5 and 4.5 dS m-1), with five replicates. Plants were grown in pots containing 10 dm3 of soil for 80 days. The reduction in the photosynthetic rate of cowpea varieties occurs mainly due to the decrease in stomatal conductance caused by salt stress. Salt stress increased the electron transport rate and photochemical quenching of cowpea varieties, but stress-tolerant varieties increased the CO2 assimilation rate and instantaneous carboxylation efficiency. The Ceará, Costela de Vaca, Pingo de Ouro, Ovo de Peru, and Sempre Verde varieties are tolerant to salt stress. Salt stress decreases 26% of the production of tolerant varieties to salt stress and 54% of susceptible varieties. The present findings show the existence of variability for saline stress tolerance in traditional varieties of cowpea and that Ceará, Costela de Vaca, Pingo de Ouro, and Ovo de Peru varieties are more suitable for crops irrigated with saline water.

RESUMO

The scarce availability of good quality water for irrigation in semi-arid regions leads to the reuse of waters, such as reject brine. Associated with this, the use of alternatives, such as hydroponic cultivation in substrates suitable for the development of profitable crops, such as watermelon, a species considered moderately sensitive to salinity, will allow new opportunities for communities assisted by desalination plants. An experiment was conducted in a plastic greenhouse to evaluate the growth, physiological responses, yield, and fruit quality of 'Sugar Baby' mini-watermelon cultivated in a hydroponic system with reject brine from desalination plants and different substrates. The experimental design was randomized blocks, with treatments arranged in a 5 × 4 factorial scheme, corresponding to five mixtures of reject brine (9.50 dS m-1) and tap water (0.54 dS m-1) applied to mini-watermelon plants, in an open hydroponic system, with four types of substrate and four replicates, with two plants per plot. Mini-watermelon plants grown in coconut fiber substrate showed the best growth and production. On the other hand, washed sand was the substrate that most hampered the development of plants in all mixtures. The use of reject brine to prepare the nutrient solution reduced the growth and production of mini-watermelon, mainly in mixtures with salinity above 4.00 dS m-1. The changes in gas exchange caused by salt stress in mini-watermelon were of stomatal nature. Mini-watermelon has high energy stability under conditions of salt stress.

Assuntos

Citrullus , Hidroponia , Salinidade , Sais

RESUMO

Magnesium has been implicated in the pathogenesis of hypertension, but the role of its intracellular levels in cardiovascular diseases is not clear yet. We investigated the relationships of low concentrations of serum magnesium (sMg) and intracellular Mg (iMg) with clinical and vascular parameters. Thiazide-treated hypertensive women were separated into two groups according to lower (<2.0 mg/dL) or normal (≥2.0 mg/dL) sMg concentrations. The same patients were later divided according to lower (<3.75 mg/dL erythrocytes) and normal (≥3.75 mg/dL erythrocytes) iMg concentrations. Carotid ultrasound, radial applanation, and peripheral arterial tonometry were performed in all patients. Low sMg levels were associated with increased Framingham Risk Score (16% ± 3% vs 11% ± 1%; P = .024), higher systolic (148 ± 7 vs 135 ± 3 mm Hg; P = .049) and diastolic (91 ± 3 vs 84 ± 2 mm Hg; P = .042) blood pressure, and carotid intima-media thickness (0.92 ± 0.09 vs 0.76 ± 0.02 mm; P = .023). Low concentrations of iMg were related to wave reflection parameters such as increased augmentation pressure (20 ± 2 vs 15 ± 1 mm Hg; P = .032) and augmentation index (43% ± 2% vs 33% ± 2%; P = .004). In conclusion, in these diuretic-treated hypertensive women, low sMg was associated with higher blood pressure values, and more intense wave reflection were closely linked to iMg depletion, processes that might contribute to hypertension and other cardiovascular risk factors.

Assuntos

Hipertensão/tratamento farmacológico , Deficiência de Magnésio/tratamento farmacológico , Magnésio/uso terapêutico , Inibidores de Simportadores de Cloreto de Sódio/uso terapêutico , Doenças Vasculares/tratamento farmacológico , Adulto , Idoso , Anti-Hipertensivos/uso terapêutico , Pressão Sanguínea/fisiologia , Estudos Transversais , Método Duplo-Cego , Feminino , Humanos , Hipertensão/epidemiologia , Hipertensão/metabolismo , Magnésio/sangue , Deficiência de Magnésio/sangue , Deficiência de Magnésio/epidemiologia , Pessoa de Meia-Idade , Prevalência , Estudos Prospectivos , Fatores de Risco , Doenças Vasculares/epidemiologia , Doenças Vasculares/metabolismo , Rigidez Vascular/fisiologia

RESUMO

Many factors have been implicated in the pathogenesis of hypertension, including changes in intracellular concentrations of calcium, sodium, potassium, and magnesium. There is a significant inverse correlation between serum magnesium and incidence of cardiovascular diseases. Magnesium is a mineral with important functions in the body such as antiarrhythmic effect, actions in vascular tone, contractility, glucose metabolism, and insulin homeostasis. In addition, lower concentrations of magnesium are associated with oxidative stress, proinflammatory state, endothelial dysfunction, platelet aggregation, insulin resistance, and hyperglycemia. The conflicting results of studies evaluating the effects of magnesium supplements on blood pressure and other cardiovascular outcomes indicate that the action of magnesium in the vascular system is present but not yet established. Therefore, this mineral supplementation is not indicated as part of antihypertensive treatment, and further studies are needed to better clarify the role of magnesium in the prevention and treatment of cardiovascular diseases.