Effects triggered by foliar selenium application on growth, enzyme activities, mineral nutrients and carbohydrates in lettuce under an aquaculture system

Se has beneficial effects on plants, through the stimulation of plant productivity, the reduction of abiotic stresses, and the improvement in N metabolism. Therefore, we investigated the effect of the foliar application of different concentrations of Se (0, 4, 8 and 16 μmol L-1) on lettuce plants grown in an aquaponics system (fish water) compared with a control (conventional soilless fertigation). The NO3- concentration supplied by the fish water was 47% of the control solution. The results showed a reduction in the fresh weight of lettuce plants irrigated with the fish water mixture treatment, along with an increase in sugar concentration. However, the application of Se at 4 and 16 μmol L-1, prompted a relief of this stress, reducing both lipid peroxidation and the sugar content, and increasing the nitrate concentration. In addition, in the case of the highest concentration of Se (16 μmol L-1), the values of nitrate were comparable those control plants. We show the importance of sprayed Se in increasing the efficiency of N utilization, in addition to lessening environmental issues for aquaponics culture.