Metabolism of nitrate- and ammonium-nitrogen absorbed from ammonium nitrate and ammonium sulfate in the tobacco plant

In water culture experiments with tobacco plants, ammonium nitrate has been generally used as a nitrogen source. In a comparison among various nitrogen sources for water cultured tobacco, better growth has been obtained with ammonium nitrate than with sodium nitrate and ammonium sulfate (1). It has been shown that both ammonium- and nitrate-nitrogen are simultaneously absorbed by the tobacco plant from ammonium nitrate (2). It has been also apparent that physiological toxicity developed when ammonium-nitrogen was absorbed from ammonium sulfate. It has been considered that this toxicity developed by the abnormal metabolism of ammonium-nitrogen in the plant. No toxicity appears to develop when ammonium-nitrogen is absorbed from ammonium nitrate. In the present paper, the metabolism of ammonium- and nitrate-nitrogen absorbed from ammonium nitrate and ammonium sulfate in the tobacco plant was investigated.