Evaluation of vitamin C, nitrate and chlorophyll content determined in lettuce (Thaís, Vanda, Verônica) cultivated in hydroponic system using wastewater

The objective of this work was to determine the levels of vitamin C, nitrate and chlorophyll in three lettuce cultivars in a hydroponic system using waste- and well-water. The experiment was conducted in a hydroponic system using laminar flow technique and nutrients in a protected environment. The experimental design was randomized blocks with treatments set up in split-plots with three replications, whose main plots devoted to lettuce cultivars and sub-plots to hydroponic solutions. The experimental solutions consisted of 7 nutrients (S): S1=Furlani solution, S2=domestic wastewater, S3=optimized domestic wastewater, S4 =well water S5 =optimized well water; S6 = reactor wastewater solution and S7 =optimized reactor wastewater solution and the subplot for the three cultivars of iceberg lettuce (Verônica, Vanda, and Thais). The following variables were determined: nitrate, vitamin C and chlorophyll content using the method described by Lichtenthaler. The results indicated that highest content of vitamin C was found in the Vanda cultivar using the S1 solution. For Veronica cultivar, the highest levels of vitamin C were observed at solutions S1, S2, S3, S4, and S7. The solutions S2 and S3 did not differ from one another in all three cultivars. For the Vanda cultivar, solutions S1, S4 and S7 were the ones that promoted the highest levels of nitrate, 4.61; 3, 32 and 2.64 g kg-1, respectively. Evaluating the effect of the solution within the cultivars, we verified that the highest nitrate values obtained from S2 nutrition for cultivars Thais and Verônica. Regarding the S5 solution, the Verônica cultivar presented the highest concentration of this nutrient. The cultivate Thaís, the highest contents of chlorophyll b were found in solutions S7, S6, S4, S3 and S2, where they did not differ significantly. Regarding to Vanda cultivar the highest values of chlorophyll b were present in solutions S2 and S5. The Verônica cultivar independent of the solution used presented the same values of this pigment.