Evaluation of Nitrate Accumulation and Nitrate Reductase Activity in Different Vegetative Growth of Selected Iranian Land Races of Spinach (Spinacia oleracea L.)

An outdoor pot experiment was carried out in sand+ coco-peat culture (80:20 ratio) to investigate the response of nitrate reductase activity and nitrate accumulation in roots and leaves of fifteen Iranian landraces of spinach (Spinacia oleracea) at different stages of plant development. Plants were tested during a three periods from 22, 30 and 38 days after emergence of first true leaves and before flowering. Results showed that the highest activity of nitrate reductase (51.29 µM NO-2. g-1.h-1) was found in the leaves of ‘Tabriz’ at the first vegetative stage and in roots of ‘Qazvin’, ‘Saleh Abad-e- Qom’ and ‘Qom’ plants at the third vegetative stage(20.71, 15.27, 15.34 µM NO-2. g-1.h-1, respectively). Lowest activity of nitrate reductase in leaves were found in plants of ‘shiraz’ in third vegetative stage(1.56 µM NO-2. g-1.h-1). Nitrate reductase activity were significantly lower in roots of ‘Birjand’ in first vegetative stage compared to other land races (3.85 µM NO-2. g-1.h-1). Leaves of ‘Qazvin’ have the highest nitrate content at the third vegetative stage(7122 µM NO-3. g-1 dry weight). Nitrate accumulation in leaves of ‘Arak-1’ were found lower than other land races in second vegetative stage (2961 µM NO-2. g-1.h-1). Nitrate content in roots of ‘Varamin-1’ were higher in 2 th vegetative stage(3741 µM NO-2. g-1.h-1). Significant differences in the nitrate reductase activity and nitrate accumulation were observed in selected Iranian land race of spinach. As, the nitrate levels in spinach should be kept as low as possible while near maximum yields are maintained, this can be accomplished by planting selected land races of spinach that are selected based on nitrate reductase activity and nitrate content analyses.