Influence of Sulphur Deficiency on Metabolism of Black Mustard

Abstract

1. The effects of sulphur deficiency on the size of black mustard plants was evident early, but chlorosis of the leaves appeared late. The main symptoms were the short plants, the yellow-green color of the upper leaves, the small leaves and the thin stems. The stems were hard and the leaves had a stiff texture. Anthocyanin development in leaves and stems, the hairy nature of these organs, and the pimply character of the young leaves were prominent. The weight of the tops was reduced more than that of the roots, causing a low top-root ratio; but of the tops the stems were affected more than the leaves. Stem elongation was not prominent. 2. The sulphur-deficient stems were low in moisture. They were very high in ammonia, amino acids, and amides. Nitrates accumulated to a certain extent. The minus-sulphur stems were very low in reducing sugars, but they were much higher in sucrose and starch and also somewhat higher in acid-hydrolyzable carbohydrates than the stems of the plus-sulphur plants. Little volatile sulphur was found in the sulphur-deficient stems. 3. The chemical composition of the sulphur-deficient stems seemed to be due mainly to the combined influences of proteolysis and poor reductase activity. The breakdown of proteins accounted mainly for the accumulation of ammonia, amides, and amino acids, although this was no doubt partly the result of reduced protein synthesis owing to deficiency of sulphur-containing amino acids. Slow reduction of nitrates caused their accumulation and the resulting poor nitrate utilization for the accumulation of sucrose, starch, and acid-hydrolyzable carbohydrates. The accumulation of these carbohydrates accounted for the hard stems and stiff texture of the leaves. Proteolysis is usually accompanied by decrease in the carbohydrates. This was true in the present work to the extent that the reducing sugars were low in the minus-sulphur stems. 4. The effects of sulphur deficiency on plants in general are summarized and compared.

Abstract

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