Brief Papers Commiients on the Absorption of Inorganic Ions by Root Celilsi

The findings of modern microscopy reveal a seemingly unlimited physical organization in living protoplasm. At the same time, they point up the extreme lability of many protoplasmic structures. For example, the endoplasmic reticulum, a continuous network of membrane-bound cavities that permeates the cytoplasm of animal cells, breaks down on injury or cytolysis into a collection of isolated vesicles (10). Also, it is well known that structures such as the mitochondria may be profoundly altered as a result of cellular changes or variations in experimental conditions (1). In terms of organic chemistry, the structures of the protoplast are equally elaborate. From even a cursory survey of plant biochemistry one is impressed by the extreme complexity of living structures and by their instability or transitory nature. In the present communication, the writer wishes to point out that much of the puzzling information concerning the absorption of inorganic ions by plant tisstues becomes more comprehensible when viewed in terms of protoplasmic structures. That is, the mineral absorption and isotopic exchange data regarding root tissues suggest that inorganic ions may be laid down as component units of highly complex and unstable chemical arrangements in cells. Certain of the ideas to be presented are similar to those put forth a decade ago by Steinbach on the basis of the behavior of inorganic ions in striated muscle cells (11). A few examples of the mineral absorption data will serve to present the general concept. It has been commonly observed that many plant tissues lose absorbed ions such as K+ to dilute solutions of HCl. With barley root tissue, essentially all of the absorbed K+ is released in a two-hour period to HCl solutions of normality 10-3 or greater (7). A further significant aspect of the K+ release is the concomitant and proportionate loss of a variety of other cellular constituents such as inorganic phosphorus, soluble organic phosphorus, soluble nitrogen, and Ca++ (7). That is, hydrogen ion concentrations that induce the relea:se of a particular absorbed ion also effect a release of all other absorbed cations and anions as well as certain organic components of the cell. Conceivably, this experimental observation could be explainedl as the result of an effect of hydrogen ion on the properties of certain cytoplasmic membranes. In the writer's opinion, it could be equally well explained on the basis of an instability to H+ of a chemical structure in which all of the absorbed ions are represented.