Inorganic Phosphorus in Plant Substances. an Improved Method of Estimation

In the synthesis of organic phosphorus compounds by the plant and in their storage in the seed as reserve food the inorganic phosphates play an important part. The phosphorus used in this synthetic process is taken into the plant in inorganic form and used in the building up of complex organic phosphorus compounds such as lecithins, phosphoand nucleo-prot,eins and salts of phytic acid. It is believed by some investigators that unmodified plant tissue and a large number of the seeds contain practically no phosphorus in inorganic combination. Since inorganic phosphate is the starting point in the synthesis of organic phosphorus compounds and since there exist in the plant enzymes which have the property of splitting off inorganic phosphorus from such compounds, it would seem probable that at least an appreciable quantity of phosphorus in inorganic form might be found in such plant tissues and seeds. At any rate, such a supposition has been well sustained in a previous paper from this laboratory by E. B. Forbes, A. Lehmann, R. C. Collison and A. C. VVhittier, in which was included the original acid alcohol method of inorganic phosphorus estimation. Methods of estimating inorganic phosphorus in plant substances usually begin wit’h some means of acid extraction of the material with subsequent separation of the phosphates from the extract. Some of the proposed methods may be questioned on the ground of mechanical imperfection and also because they do not take into sufficient consideration the influence of organic matter on the precipitation of phosphates with the common precipitating agents. This influence on precipitation was investigated two years ago in