Characterization of nitrate reductase activity (NR) in foliar and radicular tissues of Physalis angulata L.: Diurnal variations and protocol optimization

Abstract

Nitrate reductase (NR) is the first enzyme in the nitrogen assimilation pathway. The determination of its activity requires modifications for each plant species. The goal of this work was to evaluate the variation of NR activity throughout the day and the optimization of assay conditions in foliar and radicular tissues of Physalis angulata. The analysis was done in plants cultivated in a hydroponic system at two months of age. The NR activity was based on the in vivo assay method. Enzyme activity was observed on leaf and root, indicating two sites of nitrate assimilation with a higher activity in the daylight in leaf. The NR activity in leaf was increased after 4h of luminosity. In the root, we observed a high activity during most of the day, especially in periods of higher solar radiation and temperature. To obtain the highest activity of NR in both tissues we suggest 1% n-propanol, 50mM of KNO3- in pH=7 phosphate buffer for 75 min incubation in water bath.