Iron in higher plants: Storage and metabolic role

Abstract

Iron in the earth's crust is more oxidized now than it was when life evolved. Generally iron is available in the soil in the ferric form but must be taken up and utilized in the ferrous form. While iron is essential for life in small amounts, higher concentrations are toxic. Plants store iron for future use as ferritin which is ferric phosphate coated with protein. The protein coat apparently prevents iron toxicity or use of stored iron by pathogens. Iron is found in both heme‐proteins (cytochromes, catalase, etc.) and non‐heme proteins (ferridoxins, nitrite reductase, etc.). These enzymes are characterized by involvement in oxidation‐reduction reactions involving electron or proton transfer. One might say that life evolved around iron.