The physiological assessment of the nutrient status of plants. III. Experiements with plants raised at different nitrogen levels.

Abstract

Young subterranean clover plants were raised at several levels of nitrogen supply, and then transferred to complete solutions and to solutions without nitrogen Subsequent leaf area response patterns were not related to the supply of combined nitrogen before transfer. The relative differences m leaf area between the two solutions were thought to depend on differences In nodulation caused by differences In the supply of combined nitrogen before transfer. Further experiments showed that the rates of leaf area Increase of inoculated and well-nodulated plants In solutions without nitrogen were similar to those of corresponding plants receiving combined nitrogen Plants that had not been inoculated showed markedly smaller leaf growth rates after transfer to solutions without nitrogen than in complete solutions Even when the previous supply of combined nitrogen had been adequate, plants transferred to solutions without nitrogen were unable to maintain leaf area Increases at rates comparable with those of the corresponding plants in complete solutions for more than 3 days. Reasons for the marked differences between these results and those of experiments with phosphorus, sulphur, potassium, and boron are discussed