Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Sulfur is an essential element for growth and physiological functioning of plants, however, its content strongly varies between plant species and it ranges from 0.1 to 6 % of the plants'' dry weight. Sulfate taken up by the roots is the major sulfur source for growth, though it has to be reduced to sulfide before it is further metabolized. Root plastids contain all sulfate reduction enzymes, however, the reduction of sulfate to sulfide and its subsequent incorporation into cysteine takes predominantly place in the shoot in the chloroplast. Cysteine is the precursor or reduced sulfur donor of most other organic sulfur compounds in plants.