The Influence of Nitrogen in Nutrient Solution on Growth, Nutrient Uptake and Enzymatic Activity of Anacardium othonianum Rizz

The availability of nutrients directly affects plant growth and development, with nitrogen being one of the most necessary nutrients in metabolism in general. Using the hypothesis that Anacardium othonianum Rizz. can be physiologically affected by different doses of nitrogen, this study aimed to evaluate aspects of growth, nutrient absorption and enzymatic activity during the production of seedlings of this species in hydroponic cultivation. The doses of 0.0, 2.5, 5.0, 7.5, 10.0, 12.5 and 15.0 mmol l^–1 of N were tested. At 120 days after transplanting the seedlings into the nutrient solution, it was observed that doses higher than 10.0 mmol l^–1 of N may constitute an excess, negatively affecting the number of leaves and leaf area. The enzymes glutamine synthetase and nitrate reductase showed greater activity in seedlings subjected to 2.5 mmol l^–1 of N. Doses higher than this negatively affected the activity of these enzymes, indicating that A. othonianum Rizz. may be a species sensitive to ammonia. Alternatively, the absence of N (0.0 mmol l^–1) stimulated ischolar_main mass accumulation, absorption of K, Mg and B ions, as well as nitric oxide synthesis. The present study contributes to obtain healthy seedlings and to the knowledge of the metabolism aspects of an important Cerrado fruit tree.