Some Effects of Ammonia on Plant Metabolism and a Possible Mechanism for Ammonia Toxicity

Plant injury has been traced to ammonia derived from organic sources such as urine (9), chicken manure (8), cottonseed meal (12) and animal manure (3). In addition, inorganic sources such as aqua ammonia, anhydrous ammonia, and ammonium salts have been reported injurious to plants when placed too close to the root zone (3, 7). The toxicity of ammonia to animals has been demonstrated by Sumner (10). The injection of urease into rabbits resulted in death of the animals when NH, in the blood rose to 5 mg per 100 ml and before any change in blood pH could be detected. Ammonia and ammonium co-mpounds are being used as fertilizers in increasing amounts. Therefore the question of how ammonia produces the toxic symptoms which frequently result from its use on plants becomes a matter of practical as well as theoretical interest. The object of this work was to study the effect of ammonia on plant metabolism with the view of locating one or more sites at which ammonia could be shown to have a deleterious effect on the normal metabolic processes of plants.