Root uptake either by excised roots or by intact young plants (3-4 week old) showed linearity in the period from 30 to 180 minutes of contact with the solution. Km values were the same for both varieties being, however, slightly lower in the case of excised roots. Foliar uptake was affect neither by source (monoammonium against diammonium phosphate) nor by the presence of urea in the same solution.