Sulfur is present in the structure of important amino acids such as cysteine and methionine, so it is essential in the creation of proteins in which, in addition to this role, participates in the creation of proteins thanks to the disulfide bridges (S-S) that are formed between the different amino acids present in them.
Cysteine is found in glutathione, which in turn creates phytochelatins, which are proteins with the ability to chelate heavy metals such as cadmium, and thus act as a defense mechanism for plants against these toxic agents. Glutathione is also necessary for the defense of pathogens.
Sulfur is also a structural element of thiamine or vitamin B1, an essential compound of coenzymes that catalyze the oxidation of pyruvic acid in the respiratory cycle.
Sulfur is absorbed by roots and leaves in the inorganic form as SO4-2 ion. It is then reduced and incorporated into organic compounds, where it is mineralized by microorganisms.
It can also be absorbed by the stomata of the leaves as sulfur dioxide (SO2), an air pollutant resulting from the combustion of coal, wood and oil. The SO2 reacts with the water inside the cells creating bisulfite (HSO3-), which displaces the chlorophyll magnesium and thus decreases photosynthesis.
Sulfur deficiencies are not common since sufficient amounts are present in the soil. But if this deficiency occurs, the plants suffer less growth and become stiff and brittle. Sulfur deficiency can be confused with a lack of nitrogen, both have widespread chlorosis in the leaves. Unlike nitrogen deficiency, the symptoms of its deficiency initially appear in young leaves, due to the immobility of sulfur