Cooling and concentration of nutrient solution in hydroponic lettuce crop

The study was conducted in greenhouse at horticulture department of the Instituto Federal do Espirito Santo, Campus Itapina, Colatina, northwestern Espirito Santo state, Brazil, with the objective of evaluating the effect of cooling and electrical conductivity of nutrient solution on growth and development of lettuce cv. Vitoria de Santo Antao in hydroponics. The study was conducted in a completely randomized design with two factors (control of the maximum temperature of the nutrient solution: 26 degrees C and without control; and electrical conductivity, EC, of the solution: 1, 2 and 3 dS m(-1)) with three repetitions. The plants were harvested fifty-two days after sowing (DAS). We evaluated the dry and fresh mass of leaves, stems and roots, stem and root length, root volume and plant water content (%). The temperature of the nutrient solution influenced the behavior of lettuce influenced by the electrical conductivity, showing that the increase of the EC did not reduce the lettuce productivity when the maximum temperature of the nutrient solution is limited, which in this experiment was tested at 26 degrees C. The cooling of the nutrient solution provided greater accumulation of mass and a higher water percentage in plants, increasing the productivity of hydroponic lettuce in tropical climate.