Sulfur is a constituent of three amino acids (cystine, methionine and cysteine) and is therefore essential for protein synthesis. It is essential for nodule formation on legume roots. Sulfur is present in oil compounds responsible for the characteristic odors of plants such as garlic and onion.
The function in the plant and the deficiency symptoms of sulfur are very similar to nitrogen. Deficient symptoms in plants are: young leaves light green to yellowish in color. In some plants, older tissue may be affected also. Small and spindly plants. Retarded growth rate and delayed maturity.