ACCUMULATION OF NITROGEN COMPOUNDS AND NITRATE REDUCTASE ACTIVITY IN LETTUCE CULTIVATED IN DIFFERENT CROP SYSTEMS ACÚMULO DE COMPOSTOS NITROGENADOS E ATIVIDADE DA REDUTASE DO NITRATO EM ALFACE PRODUZIDA EM DIFERENTES SISTEMAS DE CULTIVO

Abstract

Nitrate content determination is important for food quality evaluation , therefore when ingested nitrate is reduced the nitrite, which can generate harmful compounds to the human organism. Ahead of this, the present work had as objective to study the transport and accumulation of nitrogen compounds and the nitrate reductase activity in lettuce cultivar 'Vera' produced in Registro (SP) in different cropping systems . W ere collected samples of the xylem sap, aerial part and root for quantification of nitrogen compounds and of the reductase activity in vivo . The nitrate concentration in the xylem sap , the nitrate and amino acids contents, as well as the nitrate reductase activity , demonstrated more intense transport, accumulation and assimilation in plants cultivated in in hydroponic solution , followed of the conventional system and finally, of the organic. The stem of the plant in the three systems of culture presented high capacity of accumulation and assimilation the nitrogen compounds . The nitrate reductase activity in leaves was superior of the root. The content nitrate, independent of the culture system, varied of 24.32 the 800.06 mg kg -1 of FW in the different parts of the plant. However, it did not exceed the maximum limits recommended by literature. KEY-WORDS: Vegetables; quality ; nitrite; metabolism of nitrogen.