Chlorosis, a yellowing of the plant leaf due to a lack of chlorophyll, may be caused by a variety of factors. Among the more common causes are compacted soils, poor drainage, root damage, alkaline soils, and nutrient deficiencies. Probably the most common cause is iron chlorosis, where iron is unavailable to the plant. Iron (Fe) is an essential element for plant growth. It is required for the formation of chlorophyll, the green pigments that capture light to produce food for the plant. Iron is also necessary for the proper functioning of many plant enzyme systems that influence respiration and plant metabolism.