Nitrate reductase activity in the different phenophases of 'palmer' mango cultivated in the semiarid

Nitrate reductase is the enzyme that catalyzes the first reduction reaction in the nitrate assimilation process, an important nitrogen (N) source. This element is one of the macronutrients required in greater amounts by mango (Mangifera indica L.), exerting a great influence on the growth and development of the plants. In this context, this work aimed to evaluate nitrate reductase activity (NRa) throughout the day and characterize it in leaves of 1st and 2nd vegetative flushes and young roots of 'Palmer' mango cultivated in the Brazilian semiarid For each phenophase, leaves and roots were randomly collected from six plants in the orchard. A completely randomized design was employed, with four replications, and the NRa quantification was based on the in vivo evaluation method. The enzyme activity was maximum in the period of greatest solar radiation or from 10 a.m. to 11 a.m. The 2nd flush leaves and young the roots constitute the main nitrate assimilation sites in the mango crop in comparation with 1st flush leaves. Fertilization with nitrate or potassium sources in the different phenological phases benefit the NRa, which remains maximum during reproductive phase than vegetative phase.