Absorption of Sulfur Dioxide From the Atmosphere by Cotton Plants

Cotton plants were grown in nutrient solutions containing 0.1, 2, 5, 10, and 50 ppm. sulfate. Atmospheric sulfur dioxide was excluded from the roots and the sulfate in the nutrient solution was labeled with S35 to permit determination of the amount of sulfur which was absorbed by the plants directly from the atmosphere. Growth and sulfur content of the plants were sensitive functions of the concentration of sulfate in the nutrient solutions. The data indicate that sulfur dioxide was absorbed by the growing plants directly from the atmosphere. The amount absorbed was roughly proportional to the size of the plant and was presumed to be a function of the effective leaf surface. According to the data, healthy cotton plants obtained about 30 per cent of their sulfur from the atmosphere. Over 50 per cent of the sulfur in sulfur-deficient plants was apparently absorbed directly from the atmosphere. For satisfactory growth of the cotton plants, the sulfur dioxide of the atmosphere was inadequate as the sole source of sulfur. Nevertheless, atmospheric sulfur dioxide contributed a large percentage of the sulfur taken in by the plants, and it is concluded that, under the conditions of the experiment, absorption of sulfur dioxide providedmore » an important supplementary source of sulfur to the growing plants.« less