A B S T R A C TThe objective of this study was to evaluate the growth and accumulation of ions in lettuce grown in different hydroponic systems and recirculation frequencies. The experimental design was randomized blocks with 8 treatments and 4 replicates. The evaluated hydroponic systems were Nutrient Flow Technique (NFT) and an adapted Deep Flow Technique (DFT), the latter with recirculation frequencies of 0.25, 2 and 4 h. Both systems used fresh water and brackish water. Plant growth, accumulation of inorganic solutes (Na + , K + , Cl -and NO 3 -) and the correlation between dry matter production and Na + /K + and Cl -/NO 3 -were evaluated. The salinity of the water used to prepare the nutrient solution caused decrease in growth and K + and NO 3 -levels, and increased contents of Na + and Cl -in the plants. When using fresh water the highest dry matter production was obtained in the NFT system. In case of brackish water the adapted DFT system increased the production, in relation to NFT system (at same recirculation frequency: 0.25 h). It was found that the choice of the type of hydroponic system and recirculation interval for the cultivation of lettuce depends on the quality of the water used to prepare the nutrient solution.Teor de solutos inorgânicos em alface cultivada com água salobra em diferentes sistemas hidropônicos R E S U M O Objetivou-se, neste trabalho, avaliar o crescimento e o acúmulo de íons em alface cultivada em diferentes sistemas hidropônicos e frequências de recirculação. O delineamento experimental foi o aleatorizado em blocos com 8 tratamentos e 4 repetições. Os sistemas hidropônicos avaliados foram a Técnica do Fluxo Laminar de Nutrientes (NFT) e a Técnica do Fluxo Profundo (DFT) adaptada, este último com frequências de recirculação de 0,25, 2 e 4 h. Foi utilizada, em ambos os sistemas, água doce e água salobra. Foram avaliados o crescimento, o acúmulo de solutos inorgânicos (Na + , K + , Cl -e NO 3 -) e a correlação entre a produção de matéria seca e a relação Na + /K + e Cl -/NO 3 -. A salinidade da água utilizada no preparo da solução nutritiva proporcionou diminuição no crescimento e nos teores de K + e NO 3 -e aumentou os teores de Na + e Cl -nas plantas. Quando foi empregada água doce, o sistema NFT proporcionou maior produção de massa de matéria seca. No caso de água salobra o sistema DFT adaptado aumentou a produção, em relação ao sistema NFT (na mesma frequência de recirculação: 0,25 h). Verificou-se que a escolha do sistema hidropônico e do intervalo de recirculação para o cultivo da alface depende da qualidade da água utilizada no preparo da solução nutritiva.

Amaranthus cruentus L. is a forage species, with grains that exhibit excellent nutritional characteristics, being the 'BRS Alegria' the first cultivar recommended for cultivation in Brazil. This study aimed at evaluating the effect of salt stress on the growth and concentrations of organic and inorganic solutes in Amaranthus cruentus L. ('BRS Alegria' cultivar). Height, stem diameter, number of leaves, leaf, stem and root dry mass, leaf area, relative water content and membrane integrity percentage, as well as soluble carbohydrate, free amino acid, soluble protein, free proline, Na+, Cl- and K+ contents, were evaluated in different plant organs. Salinity significantly reduced the biomass yield and leaf area from the treatment with 25 mM of NaCl, indicating that the 'BRS Alegria' cultivar is sensitive to salt stress. Soluble carbohydrates in the leaves decreased by 59 %, while the other organic solutes showed no substantial increases. These results, coupled with the reduction in the relative water content and membrane integrity, suggest a low ability of this cultivar to adjust osmotically under salt stress. The K+/Na+ ratio abruptly decreased in 25 mM of NaCl, suggesting an ionic imbalance, which may partially explain the salt-induced growth reduction.

Salinity is still one of the main factors that limit the growth and production of crops. However, currently, hydrogen peroxide (H 2 O 2) priming has become a promising technique to alleviate the deleterious effects caused by salt. Therefore, this study aimed to test different leaf spraying strategies with H 2 O 2 for acclimation of sunflower plants to salt stress, identifying the main physiological and biochemical changes involved in this process. The experiment was conducted in a completely randomized design, with four replications. Initially, four concentrations of H 2 O 2 were tested (0.1; 1; 10 and 100 mM) associated with different applications: 1AP-one application (48 h before exposure to NaCl); 2AP-two applications (1AP þ one application 7 days after exposure to NaCl) and 3AP-three applications (2AP þ one application 14 days after exposure to NaCl), besides this two reference treatments were also added: control (absence of NaCl and absence of H 2 O 2) and salt control (presence of 100 mM of NaCl and absence of H 2 O 2). The experiment was conducted in hydroponic system containing Furlani's nutrient solution. Salt stress reduced the growth of sunflower plants, however, the H 2 O 2 priming through leaf spraying was able to reduce the deleterious effects caused by salt, especially in the 1 mM H 2 O 2 treatment with one application. H 2 O 2 acts as a metabolic signal assisting in the maintenance of ionic and redox homeostasis, and consequently increasing the tolerance of plants to salt stress.

Basil (Ocimum basilicum L.) is a medicinal species of Lamiaceae family, popularly known for its multiple benefits and high levels of volatile compounds. The species is considered to be one of the most essential oil producing plants. Also cultivated in Brazil as a condiment plant in home gardens. The objective of this study was to evaluate the effect of salinity on the growth of basil in nutrient solution of Furlani and to identify variables related to the salinity tolerance in this species. The first assay was performed with variation of five saline levels (0 -control, 20, 40, 60 and 80 mM NaCl). In the second assay six genotypes were evaluated in two salinity levels 0 and 80 mM NaCl. The height, stem diameter, number of leaves, dry mass and inorganic solutes in different organs, photosynthetic pigments, absolute membrane integrity and relative water content were evaluated. All biometric variables in basil were significantly reduced by salinity. Dry matter yield and percentage of membrane integrity were the variables that best discriminated the characteristics of salinity tolerance among the studied basil genotypes. Basil genotypes showed a differentiated tolerance among the genotypes, the 'Toscano folha de alface' being considered as the most tolerant and 'Gennaro de menta' as the most sensitive, among the species studied.

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Noni (Morinda citrifolia) is a fruit species which is well adapted to different soil and climate conditions, and may be a good option for farmers in arid and semi-arid regions. To evaluate the tolerance of noni plant in the initial phase to salinity and the accumulation of inorganic solutes in its organs, an experiment was carried out in a greenhouse under hydroponic system. The experimental design was completely randomized, with five levels of NaCl (0, 25, 50, 75 or 100 mM) in the nutrient solution, and four replicates. Plant height, stem diameter, number of leaves, dry matter of leaves, stems and roots, leaf area, leaf succulence, sclerophylly index and the contents of Na + , Cl -and K + in different plant organs were evaluated after 40 days of stress. Salinity reduced the growth of all plant organs in the initial phase, in contrast, leaf succulence and sclerophylly index increased by 32% at the highest saline level, compared with control plants. The contents of Na + and Cl -in leaves, stems and roots increased, while K + contents decreased with the increment in salinity. The highest K + contents were observed in the roots and the highest Na + and Cl -contents were observed in the leaves. Salinity induced disturbances in the ionic homeostasis of noni plants, which can explain, at least in part, the saltinduced growth reduction.

The aim of this study was to evaluate the effect of salt stress on the contents of inorganic and organic solutes, pigments and essential oil in two basil genotypes cultivated in hydroponic system. The experiment was carried out in a greenhouse. Treatments were distributed in randomized blocks, in a 2 × 2 factorial arrangement, corresponding to two contrasting genotypes (‘Toscano folha de alface’ (TFA) and ‘Gennaro de menta’ (GM)) and two salt levels (0 - control and 80 mM NaCl), with six replicates. The Na+, Cl- and K+ accumulation in the leaves, stem and roots did not differ between genotypes. Salt stress increased free amino acids accumulation in the leaves of the TFA genotype. The proline content increased in the roots of both genotypes. However, in GM genotype, the proline content (3.12 mmol g-1 dry mass (DM)) was around 2-fold greater when compared to TFA genotype (1.48 mmol g-1 DM). The salt stress increased the photosynthetic pigments content only in the GM genotype. Inorganic solutes and photosynthetic pigments content are not good indicators of salt-tolerance in the studied genotypes. Under salt stress, there was increase in oil content in GM genotype, while the TFA genotype showed a decrease compared to control treatment. In spite of showing lower oil content, the TFA genotype showed higher yield and productivity of essential oil compared to GM under salt stress conditions.

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