For a number of years workers at the Rhode Island Agricultural Experimnent Station have made chemical and agronomical studies of the quantities of nutrient mineral elements necessary to insure optimum growth of field and market garden crops. Recently attempts have been made to measure -the amounts of these elements found in the plant (3, 4) at various stages of growth as related to varying environmental conditions such as fertilization and weather factors. This localization of attack has involved the use of certain colorimetric chemical methods to measure small concentrations of nutrient elements found in the plant solution. Concentration has been extpressed as parts per million of plant solution. Since an aqueous solution is being considered, the question arose as to the influence of environmental factors such as evaporation and soil moisture upon the concentration of the plant solution. Mlight there not be sufficient fluctuations in total moisture to introduce appreciable errors in the concentrations of nutrient elements in the plant solution ? In order to answer this question it seemed necessary to make studies of the fluctuations occurring in the moisture content of the crop plant.There seemed to be two fairly clear-cut ways of attacking this problem :8 (1) To determine the water content of the extracted plant solution at various times during the growing period. (2) To determine the total moisture content of crop plants over an entire season of growth.
Moisture content of 1926 plant solutionsIn order to determine the water content of the extracted plant solution the refractometric method suggested by GORTNER and HOFFMAN (5) was used. By this method the moisture content of expressed plant tissue fluids is determined by difference, the Abbe refractometer measuring the percentage of total solids in the expressed sap in units of the sugar scale. This method is based on the fact that the refractive indices of solutions of inorganic salts and proteins in the concentrations normally present in plant sap are very nearly the same as the indices of similar solutions of carbohydrates. One or two drops of the solution expressed in the manner described by GILBERT (2) were used for each determination and the determinations were made in duplicate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.