Significance of Phloem-Translocated Organic Sulfur Compounds for the Regulation of Sulfur Nutrition

摘要: Sulfur is an essential nutrient of all living organisms. In plants, it fifth or sixth in order elemental abundance, after hydrogen, oxygen, carbon, nitrogen and phosphorus (Pitman Cram 1977; Raven 1980; 1990). Reduced-sulfur, i.e. sulfur the oxidation state -2, most important form cells. It supports specific conformations functions enzymes structural proteins via reactive sulfide moieties disulfide bonds. available for plants mainly as sulfate at roots (Rennenberg 1984). Therefore, has to be activated, reduced incorporated into carbohydrate skeletons by assimilatory reduction before can used protein synthesis (Brunold 1990, 1993). The final product cysteine. From this amino acid, other reduced-sulfur compounds, including methionine (Giovanelli 1990), glutathione (Bergmann Rennenberg 1993), S-alkylcysteine sulfoxides Liliacea., isothiocyanates Brassicacea. (Schnug 1990) phytochelatins (Rauser 1995), are synthesized a whole set metabolic pathways. plant species, sulfur/nitrogen (S/N) ratio approximately 1/20 reflects relationship these macro-nutrients (Dijkshoorn Van Wijk 1967).