A B S T R A C T The 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 . 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. R E S U M
