Abstract
The influence of the organic nitrogen on the growth of five plant species cultured in solution was examined. One amino acid selected from 20 amino acids that constitute protein was added to the culture solution as a sole nitrogen source. The growth of rice and chingensai (green pak choi, Brassica rapa var. chinesis) greatly varied with the kind of amino acid. The growth difference was smaller in wheat and cucumber than in rice or chingensai. However, the growth of soybean was not affected by the kind of amino acid. Asparagine and glutamine had a greater effect on growth than inorganic nitrogen. On the other hand, cysteine, methionine, and valine reduced the growth and nitrogen content of shoot.Then, five kinds of amino acids were selected to study the influence on the growth of rice seedlings. Glutamine increased the weight and nitrogen content of the shoot with the increase of concentration. Serine and valine was suppressed the growth of rice even at a low concentration. Since glutamine is an amino acid synthesized in the plant fertilized with inorganic nitrogen, it was suggested that glutamine was efficiently used as a source of nitrogen even at a high concentration. On the other hand, serine and valine are synthesized at the late stage of amino acid production. Therefore, it seems that they were not metabolized or accumulated in the roots, and inhibited rice growth.
