Nitrogen metabolism in pepper plants applied with different bioregulators

Certain bioregulators were studied in relation to nitrogen metabolism of pepper plants (Capsicum annuum L. cv. Lamuyo). Plants were grown under controlled conditions and submitted to regular fertilization with macro- and micronutrients. Treatments were as follows: nontreated control(TO); fosfonutren [essential amino acids and micronutrients (46.9 mg L-1)] (T1); biozyme [GA(3) (32.2 mg L-1) plus IAA (32.2 mg L-1) plus zeatin (83.2 mg L-1) plus chelated micronutrients] (T2); and GA(3) [16 mg L-1] (T3). The concentrations of NO3-, organic N, amino acids, and proteins, the activities of nitrate reductase (NR) and nitrite reductase (NiR), and finally the foliar dry weight and yield were analyzed. The results indicated that the application of certain bioregulators, such as fosfonutren (T1), which contain amino acids can cause a negative effect on the efficiency and utilization of NO3-, resulting in a drastic loss in growth and yield, even under the control treatment, in which no bioregulator was applied. On the contrary, the application of certain bioregulators based principally on the combination of different hormones, as in the case of biozyme (T2), increased NO3- assimilation under our experimental conditions, due possibly to a greater availability of these bioregulators in the leaves and increased NR and NiR activities. This appears to explain why the T2 treatment gave the greatest foliar dry weight and fruit yield per plant in the experiment.