Lime-induced iron chlorosis in citrus: Diagnosis through physiological and metabolic evidences

Abstract

Iron is essential for plants nutrition, being required in small but in critical concentrations for plant growth and crop productivity. Despite total iron content in soils is much higher than that required by plants, soil iron bioavailability is low, particularly in calcareous soils. For this, many agricultural crops worldwide growing in semiarid climates and calcareous soils suffer from iron deficiency (iron chlorosis or lime-induced chlorosis). In this sense, chlorotic leaves may contain as much or more total iron than healthy leaves of the same age (chlorosis paradox). In this chapter, we discuss the strengths and weaknesses of the leaf visual rating of chlorosis, floral mineral analysis and leaf active iron for diagnosing citrus iron nutritional status. The effect of iron chlorosis on yield and physical and chemical characteristics of citrus fruits was also reviewed. We analyse the metabolic response of citrus to iron deficiency, paying special attention to the inducible mechanisms developed under low-iron stress and to the metabolic changes able to be used to evaluate the iron deficiency. Finally, we reviewed the bioactive compounds in the citrus fruits, paying special attention to the fact that iron deficiency enhances phenolics and, as a consequence, health-promoting effects of the fruits for the human body.