Photosynthetic Responses, Growth, Production, and Tolerance of Traditional Varieties of Cowpea under Salt Stress.

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.

Physiological responses and production of mini-watermelon irrigated with reject brine in hydroponic cultivation with substrates.

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.

Oral magnesium supplementation improves endothelial function and attenuates subclinical atherosclerosis in thiazide-treated hypertensive women.

BACKGROUND: Epidemiological studies demonstrate an inverse association between serum magnesium and incidence of cardiovascular disease. Diuretics commonly cause hypomagneseamia. METHOD: We evaluated effects of magnesium supplementation on blood pressure (BP) and vascular function in thiazide-treated hypertensive women in a randomized, double-blind, clinical trial. Hypertensive women (40-65 years) on hydrochlorothiazide and mean 24-h BP at least 130/80 mmHg were divided into placebo and supplementation (magnesium chelate 600 mg/day) groups. Patients were evaluated for nutritional and biochemical parameters, office and ambulatory blood pressure monitoring, brachial flow-mediated dilatation (FMD), peripheral arterial tonometry, assessment of carotid intima-media thickness, central hemodynamic parameters and pulse wave velocity at inclusion and after 6-month follow-up. RESULTS: The magnesium group had a significant reduction in SBP (144 ±â€Š17 vs. 134 ±â€Š14 mmHg, P = 0.036) and DBP (88 ±â€Š9 vs. 81 ±â€Š8 mmHg, P = 0.005) at 6 months, without effect on plasma glucose, lipids, or arterial stiffness parameters. The placebo group showed a significant increase in carotid intima-media thickness (0.78 ±â€Š0.13 vs. 0.89 ±â€Š0.14 mm, P = 0.033) without change in the magnesium group (0.79 ±â€Š0.16 vs. 0.79 ±â€Š0.19 mm, P = 0.716) after 6 months. The magnesium group demonstrated a significant increase in variation of FMD vs. the placebo group (+3.7 ±â€Š2.1 vs. 2.4 ±â€Š1.2%, P = 0.015). There was a significant correlation between the intracellular magnesium variation and FMD (r = 0.44, P = 0.011). CONCLUSION: Magnesium supplementation was associated with better BP control, improved endothelial function and amelioration of subclinical atherosclerosis in these thiazide-treated hypertensive women.

Altered vascular structure and wave reflection in hypertensive women with low magnesium levels.

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.

Magnesium and vascular changes in hypertension.

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.