Salinity Of Nutrient Solution Research Articles

Produção e qualidade de mini melancia submetida ao estresse salino e razões K+/Ca2+

ABSTRACT Nutritional management can be an efficient strategy to mitigate the effects of salinity on fruit production and quality. This study aimed to evaluate the production and quality of fruits of mini watermelon crop, Sugar Baby cultivar, grown in a protected environment, under salt stress and K+/Ca2+ ratios. The study was carried out in a greenhouse, using a randomized block design, 1 + 5 scheme, resulting in six treatments and four replications. Six nutrient solutions were employed, one using low-salinity water, with NaCl (0.5 dS m-1) and standard nutrient solution (S1, control treatment), and the others using salinized water at 5.0 dS m-1 (S2) and extra addition of K (S3 = 50% and S4 = 100%) and Ca (S5 = 50% and S6 = 100%). The production (fruit production, longitudinal and transverse diameter of fruit, rind thickness, pulp firmness) and postharvest quality (soluble solids, vitamin C, titratable acidity, and maturation index), in addition to the variables related to the color of the pulp (lightness, chroma index, and Hue angle) were evaluated. The addition of NaCl reduced fruit production, longitudinal, and transverse diameter of fruit, rind thickness, and vitamin C content. Among saline nutrient solutions, extra addition of 50% K (S3) attenuates the deleterious effects of salt stress on the production variables and vitamin C content. Under salt stress, extra addition of 50% K (S3) and 100% Ca (S6) intensifies the red color of the pulp.

Effects of NaCl and CaCl2 as Eustress Factors on Growth, Yield, and Mineral Composition of Hydroponically Grown Valerianella locusta

Corn salad (Valerianella locusta) is a popular winter salad, cultivated as an ingredient for ready-to-eat salads. The application of mild salinity stress (eustress) can increase the flavor and reduce the nitrate content of certain crops but, at the same time, a wrong choice of the eustress type and dose can negatively affect the overall productivity. In this research, the effects of different isosmotic salt solutions, corresponding to two different electrical conductivity (EC) levels, were investigated on the yield and mineral composition of hydroponically grown Valerianella locusta "Elixir". Five nutrient solutions (NS) were compared, including a basic NS used as the control, and four saline NS were obtained by adding to the basic NS either NaCl or CaCl2 at two rates each, corresponding to two isosmotic salt levels at a low and high EC level. Corn salad proved moderately susceptible to long-term salinity stress, suffering growth losses at both low and high EC levels of saline solution, except from the low NaCl treatment. Hence, it appears that mild salinity stress induced by NaCl could be employed as an eustress solution and corn salad could be cultivated with low-quality irrigation water (20 mM NaCl) in hydroponic systems.

Trocas gasosas e produção em couve folha sob concentrações de Ca(NO3)2 em solução nutritiva salinizada

ABSTRACT Adequate mineral supplementation can be a strategy to enable the use of brackish water in the production of vegetables. This study intended to evaluate the effect of calcium nitrate concentrations on leaf gas exchanges and yield of kale (Brassica oleracea L) fertigated with salinized nutrient solutions. The experiment was conducted in a randomized block experimental design (4 + 1), with four replicates. Four nutrient solutions prepared in brackish water (6.0 dS m-1) containing four concentrations of Ca(NO3)2 [(750, 1,125, 1,500, and 1,875 mg L-1)] and a control treatment (standard nutrient solution using low-salinity water, 0.5 dS m-1 (750 mg L-1 of Ca(NO3)2) were used in the study. The following analyses were performed: leaf gas exchanges, leaf area, and fresh matter yield. The standard nutrient solution promoted higher values for photosynthetic rate (13.06 µmol CO2 m-2 s-1), stomatal conductance (0.19 mol H2O m-2 s-1), transpiration (2.76 mmol H2O m-2 s-1), instantaneous water use efficiency (4.73 mmol CO2 mol-1 H2O), instantaneous carboxylation efficiency (0.053 mmol CO2 mol-1 CO2), leaf area (2.78 cm2 per plant), and leaf fresh matter yield (2.64 kg per plant). The Ca(NO3)2 not nullified but mitigated the deleterious effect of salt stress on leaf gas exchanges, except for kale yield (leaf fresh matter).

Moderate Salinity of Nutrient Solution Improved the Nutritional Quality and Flavor of Hydroponic Chinese Chives (Allium tuberosum Rottler).

Sodium chloride (NaCl), as a eustressor, can trigger relevant pathways to cause plants to produce a series of metabolites, thus improving the quality of crops to a certain extent. However, there are few reports on the improvement of nutrient quality and flavor of hydroponic Chinese chives (Allium tuberosum Rottler) by sodium chloride. In this study, five NaCl concentrations were used to investigate the dose-dependent effects on growth, nutritional quality and flavor in Chinese chives. The results show that 10 mM NaCl had no significant effect on the growth of Chinese chives, but significantly decreased the nitrate content by 40% compared with 0 mM NaCl treatment, and the content of soluble protein and vitamin C was increased by 3.6% and 2.1%, respectively. In addition, a total of 75 volatile compounds were identified among five treatments using headspace solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME/GC-MS). Compared with the 0 mM NaCl treatment, 10 mM NaCl had the greatest effect on the quantity and content of volatile compounds, with the total content increased by 27.8%. Furthermore, according to the odor activity values (OAVs) and odor description, there were 14 major aroma-active compounds (OAVs > 1) in Chinese chives. The “garlic and onion” odor was the strongest among the eight categories of aromas, and its highest value was observed in the 10 mM NaCl treatment (OAVs = 794).Taken together, adding 10 mM NaCl to the nutrient solution could improve the nutritional quality and flavor of Chinese chives without affecting their normal growth.

Cultivo hidropônico de quiabeiro utilizando soluções nutritivas salinas sob aplicação de ácido salicílico

ABSTRACT The limited availability of low-salinity water for irrigation in the Northeastern semi-arid region has restricted food production, making it necessary to use strategies to reduce the effects of salt stress on plants. Among the alternatives, the foliar application of salicylic acid stands out. In this context, the objective of this study was to evaluate the effects of foliar application of salicylic acid in mitigating salt stress on the gas exchange, chlorophyll a fluorescence, photosynthetic pigments, and growth of ‘Canindé’ okra in a hydroponic system. The experiment was carried out in a greenhouse, in Pombal - PB, using the Nutrient Film Technique - NFT hydroponic system. The experimental design used was completely randomized in a split-plot scheme, with four levels of electrical conductivity of the nutrient solution - ECns (2.1, 3.6, 5.1, and 6.6 dS m-1) as the plots and four concentrations of salicylic acid - SA (0, 1.2, 2.4, and 3.6 mM) as the subplots, with four replicates and two plants per plot. SA concentration of 3.6 mM was able to minimize the effect of nutrient solution salinity on chlorophyll a fluorescence and increase the synthesis of chlorophyll b in okra plants, 34 days after transplanting. Nutrient solution salinity above 2.1 dS m-1 negatively affected gas exchange, relative water content, photosynthetic pigments, and growth and increased electrolyte leakage in the leaf blade of okra plants.

Prediction of Soluble Solids of Tomato Fruit Grown in Salinized Nutrient Solution Based on the Electrical Conductivity of the Drainage

Prediction of Soluble Solids of Tomato Fruit Grown in Salinized Nutrient Solution Based on the Electrical Conductivity of the Drainage

Salicylic acid does not relieve salt stress on gas exchange, chlorophyll fluorescence, and hydroponic melon growth.

The objective of this study was to evaluate the salicylic acid applications in attenuating the harmful effects of saline nutrient solution on the physiology and growth of 'Gaúcho' melon cultivated in the NFT hydroponic system. The experiment was conducted in a greenhouse, in Pombal-PB, Brazil. The cultivation system used was the Nutrient Film Technique - NFT hydroponics. A completely randomized split-plot design was used, with the plot referring to four levels of salinity in the nutrient solution - ECns (2.1 control, 3.2, 4.3, and 5.4 dS m-1) and the sub-plot four concentrations of salicylic acid (SA) (0, 1.5, 3.0, and 4.5 mM), applied via foliar spray, with six replications. Nutrient solution of 4.3 and 5.4 dS m-1 electrical conductivity promotes higher maximum and variable fluorescence, respectively. The stomatal conductance, transpiration, stem diameter, main branch length, leaf dry mass, and stem dry mass of 'Gaúcho' melon plants decrease with the increase in salinity of the nutrient solution. Salicylic acid increases the initial fluorescence and the main branch length of 'Gaúcho' melon plants in hydroponic cultivation. Salicylic acid at a concentration of 1.5 to 4.5 mM did not attenuate the effects of salt stress on the internal CO2 concentration, CO2 assimilation rate, and root dry mass of 'Gaúcho' melon plants.

Osmotic adjustment, production, and post-harvest quality of mini watermelon genotypes differing in salt tolerance

The mini watermelon is a crop with high yield potential in the Brazilian semiarid region; however, some problems, such as the salinity of irrigation water, can cause physiological and biochemical changes in the species, compromising production and post-harvest quality of the fruits. In the present study, two genotypes of mini watermelon (Citrullus lanatus L.) cultivated in a hydroponic system were evaluated for the effects of nutrient solution salinity on yield, fruit quality, and solutes content. The experimental design used was completely randomized, in a factorial scheme (5 × 2), with four replicates, each consisting of three plants. The mini watermelon genotypes ‘Champagne’ (CP) and ‘Fancy’ (FY) were cultivated in nutrient solutions with different electrical conductivity levels - ECsol (2.5 - control, 3.5, 4.5, 5.5, and 6.5 dS m−1). Production components, post-harvest variables of fruit quality and the contents of organic and inorganic solutes were evaluated. The increase in ECsol reduced the production variables, with the emphasis on the CP genotype, which stood out for comparatively mall production losses (45% - fruit mass); being considered tolerant to salt stress when compared to FY (57% - fruit mass). Fruit production showed a linear decrease, with a salinity threshold at 2.5 dS m−1 in both genotypes. The salinity increased the contents of total soluble solids (TSS) in both genotypes: for 9.5 to 10.6 °Brix (11.6%) in the CP genotype and from 9.7 to 12.1° Brix (24.7%) in the FY. Contents of organic and inorganic solutes, except proline, can act as indicator for the selection of salinity-tolerant mini watermelon genotypes. Despite the changes induced by salt stress in the physicochemical characteristics, the fruits remained within acceptable commercial standards for both genotypes. The FY genotype, though salt-sensitive is more suitable for hydroponic cultivation up to ECsol of 4.5 dS m−1, and both the genotypes can be used in systems up to with ECsol 6.5 dS m−1.

Optimal Nutrient Solution and Dose for the Yield of Nuclear Seed Potatoes under Aeroponics

The aeroponic production of certified seed potatoes is a booming alternative for arid and semi-arid areas where fresh water is scarce and soil-borne diseases and nematodes preclude field production. Although widely used in aeroponics, nutrient-solution salinity effects have not been evaluated in potatoes. This study aimed to (1) establish the best of two nutrient solutions (Otazú vs. modified Furlani) at 20, 50, 100, and 150% of the crop-recommended dose for seed-potato production, (2) evaluate growth indexes to diagnose plant-N status, and (3) establish a prognosis for the yield of nuclear seed potatoes under aeroponics. At 21 days after transplanting, there was a significant correlation between the nitrate-N petiole-sap test and some of the parameters measured. The 4th leaf indexes correlated with yield parameters indicating that they can be used to prognosticate the final minituber yield. The best parameters to diagnose the N status in potato plants were: 4th leaf area, length, and dry weight (Otazú’s), SPAD, and 4th leaf area (modified Furlani’s). Although both nutrient solutions had similar nitrogen concentrations, Otazú’s nutrient solution at 100% of the recommended nitrogen dose had lower salinity than the modified Furlani’s solution and was the best to produce nuclear seed potatoes.

Production and Physiological Quality of Seeds of Mini Watermelon Grown in Substrates with a Saline Nutrient Solution Prepared with Reject Brine.

The economically profitable production of crops is related, among other factors, to seed quality, the production system, and the water used in irrigation or preparation of nutrient solutions. Therefore, the objective was to evaluate the phenology, production, and vigor of seeds of mini watermelons grown in saline nutrient solution and different substrates. In the fruit and seed production phase, the experiment occurred in a greenhouse with five electrical conductivities of water for nutrient solution preparation, ECw (0.5, 2.4, 4.0, 5.5, and 6.9 dS m−1), and two growing substrates (coconut fiber and sand). We evaluated the physiological quality of seeds previously produced under the five electrical conductivities of water and two substrates. High salinities for the hydroponic cultivation of the mini watermelon cultivar ‘Sugar Baby’ accelerated fruit maturation and crop cycle, decreasing fruit size. However, in both substrates, the seed production of mini watermelons, seed viability, and seed vigor occurred adequately with a reject brine of 6.9 dS m−1 in the hydroponic nutrient solution. The seed production of ‘Sugar Baby’ mini watermelons using reject brine in a hydroponic system with coconut fiber and sand substrates is viable in regions with water limitations.

Physiology and yield of ‘Gaúcho’ melon under brackish water and salicylic acid in hydroponic cultivation

In order to study the effect of salicylic acid concentrations on the mitigation of salt stress in melon plants grown on a hydroponic system an experiment was conducted in a greenhouse at Pombal – PB, Brazil, using an NFT (Nutrient Film Technique) system. The experimental design was completely randomized, in a 4 × 4 factorial scheme, corresponding to four levels of electrical conductivity of the nutrient solution—ECns (2.1—control, 3.2, 4.3, and 5.4 dS m−1) and four concentrations of salicylic acid—SA (0, 1.5, 3.0, and 4.5 mM), with six replicates. Salicylic acid at the concentration of 3.2 mM attenuated the effect of nutrient solution salinity on the fresh weight of melon fruits. The saline nutrient solution impairs gas exchange and the relative water content and increases the intercellular electrolyte leakage in the leaf blade of melon plants. However, salicylic acid attenuates the deleterious effects of salinity and attains a maximum yield of melon fruits of 23.82 t ha−1 with foliar application of 1.5 mM at ECns of 3.1 dS m−1. Salicylic acid stimulated the synthesis of total chlorophyll, the CO2 assimilation rate, and the instantaneous water use efficiency of hydroponic melon up to a concentration of 4.5 mM. The results obtained indicate that the responses of the hydroponic melon plant grown with saline nutrient solution and the application of salicylic acid are not yet fully elucidated.

Fresh/brackish watering at growth period provided a trade-off between lettuce growth and resistance to NaCl-induced damage

Supply with fresh and brackish water at different growth periods of crops is an effective strategy to alleviate freshwater shortage and ensure food security. However, the potential mechanisms are not well understood. To bridge this gap, comparative physiological, transcriptomic and metabolomic profiling was used to analyze lettuce grown under four treatments [exposure to non-saline (NS) nutrient solution during full growth period, NS-NS; exposure to saline (S, 30 mM NaCl added to NS) nutrient solution during early, later or full growth period, S-NS, NS-S and S-S]. The results showed that after brackish water exposure, lettuce showed growth inhibition and reactive oxygen species accumulation, and the dry weight was significantly reduced under S-NS and S-S but not NS-S. NS-S saved fresh water consumption compared to NS-NS and significantly improved the brackish water use efficiency compared to S-NS and S-S. In addition, brackish water exposure regulated the antioxidant system, and activated the metabolic process related to sugar synthesis. Together, this study provides evidence of the protective roles of exposure to brackish water for only later of the lettuce growth period, and it's a valuable water supply reference for cultivating crops with brackish water in water-scarce regions.

TROCAS GASOSAS E PRODUÇÃO HIDROPÔNICA DE ABOBRINHA ITALIANA SOB ESTRESSE SALINO E APLICAÇÃO DE H2O2

ABSTRACT Knowledge about the effect of chemical conditioners on the reduction of the deleterious effects caused by salinity on crops is of great importance for the expansion of the cultivation of vegetable crops such as zucchini in the semi-arid region of the Northeast. In this context, the objective of the present study was to evaluate the effect of the foliar application of hydrogen peroxide as a mitigator of salt stress on the gas exchange, production, and postharvest fruit quality of zucchini cultivated in a hydroponic system. The study was conducted in NFT-type (Nutrient Film Technique) hydroponic system in a greenhouse, in Pombal — PB, Brazil. The experimental design was completely randomized, in a 4 × 4 factorial scheme, corresponding to four levels of electrical conductivity of the nutrient solution - ECns (2.1 (control); 3.6; 5.1 and 6.6 dS m−1), and four concentrations of hydrogen peroxide - H2O2 (0; 20; 40 and 60 μM), with three replicates. Nutrient solution with electrical conductivity above 2.1 dS m−1 caused a reduction in gas exchange and the total number of fruits of zucchini. An increase in nutrient solution salinity levels increased the total soluble solids content of the fruits and the initial fluorescence of zucchini. Under conditions of nutrient solution salinity above 2.1 dS m−1, hydrogen peroxide could not mitigate the effects of salt stress. Application of 20 μM of H2O2 when the plants were grown in a nutrient solution of 2.1 dS m−1 promoted higher total fruit weight and basal diameter of the fruits.

Hydrogen peroxide and saline nutrient solution in hydroponic zucchini culture

Saline water has been used in irrigation due to the limited availability of fresh water, especially in arid and semi-arid regions. However, the use of this type of water can affect crop growth and development. Studies have tested the use of chemical conditioners to minimize the negative effects of salinity on plants. In this scenario, the present study examined the role of hydrogen peroxide in mitigating the negative effects of salt stress on zucchini plants grown in a hydroponic system. The study was carried out in a greenhouse in Pombal - PB, Brazil. The NFT (nutrient film technique) hydroponic system was employed. A randomized complete experimental design was set up with a 4 × 4 factorial arrangement consisting of four levels of electrical conductivity in the nutrient solution (ECns: 2.1 [control], 3.6, 5.1, and 6.6 dS m-1) and four concentrations of hydrogen peroxide (H2O2: 0, 20, 40, and 60 μM), in three replicates. Foliar spraying with H2O2 at 60 and 40 μM associated with the nutrient solution of 2.1 dS m-1 increased stem diameter and root length, respectively, at 47 days after transplanting. However, at ECns higher than 2.1 dS m-1, the application of H2O2 at the concentrations of 60 and 40 μM intensified salt stress, reducing stem diameter and root length. Nutrient solution salinity levels above 2.1 dS m-1 reduce photosynthetic pigments; the number of leaves; leaf area; the length of the main branch; and the dry biomass of stems, leaves, and roots of zucchini plants. Chlorophyll b and carotenoid contents are the variables most sensitive to changes in salinity levels.

The effect of three types of aquatic plants on water purification and removal of cadmium under different salinity conditions in northwestern Iran

Abstract Phytoremediation is a high-performance and cost-effective approach to clean up contaminated water. This study aimed to investigate the rate of cadmium (Cd) uptake and changes in absorption of other elements using different plants at different cadmium concentrations under salinity conditions. This study was performed as a factorial experiment in a completely randomized design with three replications at Zanjan University located in northwestern Iran. For this purpose, three aquatic plants, Azolla Caroliniana, Watercress, and Duckweed, were used. In these experiments, different levels of Cd (0, 5, 10, 20, 40, and 80 mg L−1) in the nutrient solution as well as different NaCl concentrations (0, 10, 20, 40 and 80 mM L−1) were employed. After producing nutrient solutions with salinity and different Cd concentrations, three plants were grown in them for 30 days. The absorption of different elements such as Cd, Fe, Mn, Zn, Cu, N, P, K, Ca, Mg, and Na was measured in the plants. The results showed that the studied plants absorbed high concentrations of Cd. It was also concluded that the salinity of nutrient solution directly relates to Cd concentration in the plant tissues. The highest concentration of Cd in Azolla Caroliniana in 40 mg Cd and 80 mM NaCl was obtained with an average of 3,470.8 mg kg−1. In general, the results showed that the use of all three plants is suitable for purifying Cd-contaminated water.

Potassium nutrition as a strategy to mitigate salt stress in melon grown under protected cultivation

The use of saline water is one of the major challenges of agriculture, as it can cause nutritional imbalances and thus reduce crop yield. This study proposes to examine the efficiency of potassium nutrition as a salt stress-mitigating agent in melon grown in a protected environment. The experiment was laid out in a randomized-block design with ten treatments in a 2 × 4 factorial arrangement represented by two melon cultivars (McLaren and SV1044MF) and four nutrient solutions (S1 - standard nutrient solution, 2.5 dS m-1; S2 - nutrient solution salinized with NaCl, 5.0 dS m-1; S3 - nutrient solution salinized with NaCl + 50% K, 6.5 dS m-1; and S4 - nutrient solution salinized with NaCl + 100% K, 7.5 dS m-1). Yield (average fruit weight, production, fruit diameter, internal cavity, and pulp thickness), quality (pulp firmness, total sugars, soluble solids [SS], vitamin C, pH, titratable acidity [TA] and SS/TA ratio) and nutritional (K, Na and K/Na ratio) variables were evaluated. Plants fertigated with standard nutrient solution showed the highest values for fruit weight (1,190.6 g), production (2,381.3 g per plant), fruit diameter (13.6 cm) and pulp thickness (2.6 cm). Cultivar McLaren produced heavier fruits (931.4 g) with larger diameter (12.4 cm) and pulp thickness (2.4 cm). The addition of NaCl to nutrient solution induced a reduction in the yield variables but did not influence fruit quality. The addition of extra K to salinized nutrient solution did not mitigate the deleterious effect of salinity on the yield of melon.

Exogenous Putrescine Enhances Salt Tolerance and Ginsenosides Content in Korean Ginseng (Panax ginseng Meyer) Sprouts.

The effect of exogenously applied putrescine (Put) on salt stress tolerance was investigated in Panax ginseng. Thirty-day-old ginseng sprouts were grown in salinized nutrient solution (150 mM NaCl) for five days, while the control sprouts were grown in nutrients solution. Putrescine (0.3, 0.6, and 0.9 mM) was sprayed on the plants once at the onset of salinity treatment, whereas control plants were sprayed with water only. Ginseng seedlings tested under salinity exhibited reduced plant growth and biomass production, which was directly interlinked with reduced chlorophyll and chlorophyll fluorescence due to higher reactive oxygen species (hydrogen peroxide; H2O2) and lipid peroxidation (malondialdehyde; MDA) production. Application of Put enhanced accumulation of proline, total soluble carbohydrate, total soluble sugar and total soluble protein. At the same time, activities of antioxidant enzymes like superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase in leaves, stems, and roots of ginseng seedlings were increased. Such modulation of physio-biochemical processes reduced the level of H2O2 and MDA, which indicates a successful adaptation of ginseng seedlings to salinity stress. Moreover, protopanaxadiol (PPD) ginsenosides enhanced by both salinity stress and exogenous Put treatment. On the other hand, protopanaxatriol (PPT) ginsenosides enhanced in roots and reduced in leaves and stems under salinity stress condition. In contrast, they enhanced by exogenous Put application in all parts of the plants for most cases, also evidenced by principal component analysis. Collectively, our findings provide an important prospect for the use of Put in modulating salinity tolerance and ginsenosides content in ginseng sprouts.

Reduction of Nitrate Content in Baby-Leaf Lettuce and Cichorium endivia Through the Soilless Cultivation System, Electrical Conductivity and Management of Nutrient Solution.

Soilless cultivation systems are efficient tools to control nitrates by managing nutrient solution (NS) salinity and nitrogen availability, however, these nitrate-lowering strategies require appropriate calibration based on species/genotype-specific responses interacting with climate and growing conditions. Three experiments were carried out on lettuce and Cichorium endivia grown in ebb-and-flow (EF) and floating (FL) systems at two levels of NS salinity (EC = 2.5 and 3.5 dS m−1) (EC2.5, EC3.5, respectively) under autumn and early-spring (lettuce) and winter and late-spring conditions (C. endivia). Nitrogen deprivation (NS withdrawal a few days before the harvest) was tested at EC2.5, in the autumn and winter cycles. The EF-system caused an increase in salinity in the substrate where roots mainly develop so it mimicked the effect of the EC3.5 treatment. In the winter-grown lettuce, the EF-system or EC3.5 treatment was effective in reducing the nitrate level without effects on yield, with the EF baby-leaf showing an improved quality (color, dry matter, chlorophylls, carotenoid, vitamin C, phenol). In both seasons, the EF/EC3.5 treatment resulted in a decline in productivity, despite a further reduction in nitrate content and a rise in product quality occurring. This response was strictly linked to the increasing salt-stress loaded by the EC3.5/EF as highlighted by the concurrent Cl− accumulation. In early-spring, the FL/EC3.5 combination may represent a trade-off between yield, nitrate content and product quality. In contrast, in winter-grown endive/escarole the EC3.5, EF and EC3.5/EF reduced the nitrate level with no effect on yield, product quality or Cl− uptake, thus proving them to be more salt-tolerant than lettuce. High temperatures during the late-spring cycle promoted nitrate and Cl− uptake, overcoming the nitrate-controlling effect of salinity charged by the EF system or EC3.5. The nitrate level decreased after 3 day-long (lettuce) or 6 day-long (C. endivia) NS withdrawal. In C. endivia and EF-grown lettuce, it provoked a decrease in yield, but a concurrent improvement in baby-leaf appearance and nutritional quality. More insights are needed to fine-tune the duration of the NS removal taking into account the soilless system used and species-specific characteristics.

Physiology and production of cherry tomato cultivars in a hydroponic system using brackish water

ABSTRACT Agricultural production has become a challenge in arid and semi-arid regions due to the scarcity of water for irrigation, so brackish water is commonly used. The present study aimed to evaluate the physiological and production responses of cherry tomato cultivars under salinity levels of the nutrient solution in a hydroponic system. The experiment was conducted in a split plot and 5 × 3 factorial scheme with four repetitions. The factors corresponded to different values of electrical conductivity of the nutrient solution (ECns 2.5, 4.0, 5.5, 7.0 and 8.5 dS m-1) and cultivars (Samambaia, Tomate Vermelho and Caroline). The increase in nutrient solution salinity negatively affected the gas exchange, electrolyte leakage and photosynthetic pigments of the cherry tomato cultivars, mainly with the prolongation of stress. The photosynthetic system was efficient up to 4.0 dS m-1, but, above this electrical conductivity in the nutrient solution, there was photoinhibition or photodamage in the cherry tomato plants at 30 days after transplanting. The cherry tomato cultivars Samambaia and Caroline were the most adapted to brackish solutions, while Tomate Vermelho was the most susceptible.

Production, water-use efficiency and post-harvest quality of hydroponic mini watermelon under salinity stress1

ABSTRACT Irregularity or shortage of rainfall in semi-arid regions forces farmers to use low-quality water to irrigate crops. The present study aimed to assess the water-use efficiency and post-harvest quality of ‘Sugar Baby’ mini watermelon in response to different electrical conductivities of the nutrient solution [2.5 (control), 3.5, 4.5, 5.5 and 6.5 dS m-1], in a floating hydroponic system. The experimental design was completely randomized, with four replicates. The water consumption, production and water-use efficiency were evaluated, as well as qualitative and physico-chemical variables of the fruits. The total water consumption of the plants during the crop cycle varied between 43 (6.5 dS m-1) and 54 (2.5 dS m-1) L plant-1 among the treatments, with water-use efficiency of 0.031 kg L-1. The greatest reductions due to the nutrient solution salinity were observed for the rind thickness and fruit mass (8.80 and 5.69 %, respectively, per unit increase in dS m-1). The salinity of the nutrient solution did not influence the soluble solids content and fruit maturity index, but it had a negative effect on the pH and titratable acidity.