TOXICITY OF ALUMINUM ON SEEDLINGS AND ACTION OF CERTAIN IONS IN THE ELIMINATION OF THE TOXIC EFFECTS

The physiological action of aluminum ions in a nutrient medium has been studied in humid areas for approximately 25 years. The relative abundance in the earth of this element would suggest frequent solution of portions, but the solution tension of aluminum compounds in nature prevents appreciable quantities from reaching the ionic stage. Ithas been found, however, that aluminum occurs in nearly all seed plants, which would indicate that the hydrogen ion concentration in the immediate area of roots is not the same as its concentration in the soil mass. The toxicity of aluminum is not so easily determined as is the toxicity of the salts of the alkali and alkali earth elements. This is due to the fact that the salts of aluminum which are appreciably soluble are those of the strong acids, and these salts in turn are strongly hydrolyzed in aqueous solution, resulting in secondary formation of an acid. This in turn gives rise to hydrogen ions. The trials made may result in part from the measurement of the sum total of hydrogen and aluminum ion toxicity. This may occur in water or in soil media. MCLEAN and GIBERT (16) found that the organic compound, aluminum citrate, would in part pass through a pyroxylin membrane, and that the non-diffusible colloid portion could induce toxicity. In general the object of these experiments was to attempt to ascertain the action of aluminum on plants. It was hoped to determine: (1) the toxicity of aluminum salts of organic acids (these salts do not precipitate aluminum hydroxide when the alkalinity is raised); (2) the counter-active 'Contribution of the Massachusetts Agricultural Experiment Station no. 175.