Impact of low pH and aluminium on nitrogen uptake and metabolism in roots of <Emphasis Type="Italic">Lotus japonicus</Emphasis>

The effect of low pH and aluminum on nitrogen uptake and metabolism was studied in roots of Lotus japonicus grown in hydroponic cultures. The low pH slightly suppressed root elongation, and this effect was accompanied by the suppression of nitrate and ammonia uptake, as well as the nitrate reductase activity. In spite of high resistance of young Lotus plants to short-term Al application, the one-day treatment of Al strongly reduced nitrate uptake and also the activity of nitrate reductase (NRA) in the apical parts of roots. The glutamine synthetase activity was also suppressed by Al treatment, but in lower extent. On the other hand, the ammonium uptake and nitrite reductase activity stayed unchanged by Al treatment and the values were practically the same as in control plants. These results support the view that nitrate uptake and nitrate reduction might be the main processes responsible for Al induced growth retardation in Lotus plants grown in mineral acid soils.