SULPHUR CONTENT OF SEEDS AND SEED WEIGHT IN RELATION TO EFFECTS OF SULPHUR DEFICIENCY ON GROWTH OF SUNFLOWER PLANTS

Abstract

Introduction Detailed studies have previously been made by the writer on the effects of sulphur deficiency on the growth and metabolism of two plants, the soy bean (6) and the sunflower (7). No sulphur was intentionally added to the nutrient solution used. Yet considerable growth was made by each plant. The minus-sulphur soybean plants weighed about 70 per cent. as much as the plus-sulphur. Sulphur deficiency reduced the weight of the stems of the sunflower plants to 28 per cent. of the weight of the controls. These data show that the plants were getting considerable sulphur as an impurity. The main possible sources of this sulphur were: The sulphur in the air, part of which dissolved in the moist sand (1) and was absorbed by the roots of the plants or taken in by the plants directly from the air (16); the sulphur in the salts in the nutrient solution; and the sulphur in the seed. When plants are grown in the open there is an additional source of sulphur, the sulphur brought down by the rain (1, 8). The object of this work was to study the sulphur content of sunflower seeds as a sulphur impurity. It was thought that if the plants were grown to maturity with a minus-sulphur nutrient solution, the seeds produced would have a lower sulphur content than the seeds of plants grown with complete nutrient. By using the low-sulphur seeds it should be possible to get greater effects of sulphur deficiency than with high-sulphur seeds. As will be described presently, however, the percentage sulphur of the seeds of the sulphur-deficient plants was the same as the seeds of the plus-sulphur plants. But the former seeds were much smaller than the latter so that the problem resolved itself partly into a study of the effects of the size of the seed on the growth of the plant. The less actual sulphur present in the smaller seeds of the sulphur-deficient plants was of course one factor affecting the size of the plants produced by these seeds.