Influence of Sulphur Deficiency on Metabolism of Black Mustard

Abstract

Studies were made of the effects of growing black mustard plants, Brassica nigra, in pure quartz sand with a minus-sulphur nutrient soln. The main symptoms of S deficiency were the short plants, the small leaves, the thin stems and the yellow-green color of the upper leaves as compared with the plants grown with a complete nutrient soln. The leaves and stems of the S-deficient plants were hairy and the young leaves were pimply. The stems were low in moisture and reducing sugars but high in dry wt., in the nitrogenous fractions, nitrates, ammonia, amino acids and amides, and in the carbohydrate fractions, sucrose, starch and acid-hydrolyzable carbohydrates. The stems contained little volatile S. The low reducing sugar content and the high content of ammonia, amino acids and amides were probably due mainly to proteolysis, although the accumulation of the nitrogenous fractions may have been partly the result of poor protein synthesis resulting from the deficiency of S-containing amino acids. The accumulation of nitrates may be accounted for by the poor development of reductase and because of the slow utilization of nitrates, sucrose starch and acid-hydrolyzable carbohydrates piled up. The accumulation of these carbohydrates resulted in hard stems and stiff leaves. The discussion section of the paper contains a summary and comparison of the effects of S-deficiency on plants in general.