Source. Sulfur is present as sulfate SO42+ in mineral fraction of soil. It is also found in FeS and FeS2 forms, which are not available to plants. In industrialized areas, atmospheric sulfur dioxide (SO2) and sulfur trioxide (SO3) may be important sources of sulfur nutrition.
Regions. Sulfur in plants is required in stem and root tips and young leaves. It is remobilized during senescence.
Functions. It forms a part of amino acids cysteine, cystine and methionine. Thus it is an important constituent of some proteins, some vitamins as glutathione, thiamine, biotin and coenzyme A(CoA) and ferredoxin. The characteristic odor of cruciferous plants, onion, garlic etc. is due to the sulfur constituent of volatile oils.
Deficiency symptoms
(i) Chlorosis
(ii) Accumulation of starch, sucrose and soluble nitrogen.
(iii) While in nitrogen deficiency, chlorosis appears first in old leaves, in sulfur deficiency, young leaves are the first to be affected.
(iv) Change in pigmentation.