Toxic Effects.—The farmer knows the harmful effect of large quantities of fertilizer added to the soil. Analyses by Chauzit (see Russell, 1921) showed that Vitis vinifera began to suffer seriously as soon as 35 per cent or more lime was added. Calcium ions also have a toxic effect upon fungi (e.g., Citromyces) under neutral and basic conditions. In the grapevine, the chestnut tree, Calluna, and other plants lime chlorosis occurs with excess of calcium. A small excess of iron induces iron chlorosis in soybeans. The same metabolic disease, however, is also caused by a shortage of iron (Marsh and Shive, 1925, p. 79). The poisonous nature of aluminum is affected by H ion concentration, being intensified by an increasing H ion concentration of the soil. Below pH 5 the solubility of Al2O3 rises rapidly. In soils of more than pH 5, however, according to Magistad (1925, p. 20), lucerne, red clover, and oats suffered little from the poisonous effects of aluminum. Kaho (1926) has discussed the harmful effect of soil alkalies upon the protoplasm of plants. He was able to prove that the toxic effect depends upon the penetrating power of the ions where the anions enter the plant more abundantly than the cations. The permeability of protoplasm seems to change under the influence of different ions. (Braun-Blanquet 1932:180)
BRAUN-BLANQUET, Josias. 1932. Plant sociology: the study of plant communities. (Trans.: George D. Fuller; Henry S. Conard) New York: McGraw-Hill Book Company.