Biomassa, trocas gasosas e aspectos nutricionais de plantas jovens de ochroma pyramidale (cav. ex lamb) em resposta à fertilização nitrogenada e da interação fósforo e ambiente de luz

Abstract

The plantation of forest species requires knowledge of their nutritional requirements and irradiance. This study investigated the effects of nitrate and ammonium fertilization and the interaction between phosphorus fertilization and irradiance levels in plants of Ochroma pyramidale. The experiment were conducted at the Laboratory of Plant Physiology and Biochemistry of the National Institute of Amazonian Research along 210 and 160 days for the experiment with N and P, respectively, under greenhouse conditions. The highest dry mass values were observed in plants fertilized with ammonium when compared with the control and plants fertilized with nitrate. For gas exchange, fertilization with ammonium promoted photosynthetic rates 106% and 19%, respectively, higher than those observed in the control plants and fertilized with nitrate. The phosphorus fertilization and the increase in irradiance contributed to the increase in dry mass of the whole plant and compartments. Photosynthetic rates were also higher in plants fertilized with phosphorus and submitted to higher irradiance. This information contributes to the understanding of the responses of young plants of Ochroma pyramidale to primary factors such as availability of N, P and irradiance and suggests new research that alow to study the physiological responses of this species to different proportion NO3-/ NH4+, different dosages of P, and the interaction between N and P, as well as other levels of irradiance, both in controlled conditions and in the field.