Classification of Minerals Based on Mobility

Whether a deficiency symptom shows up first on a plant's oldest leaves or its youngest leaves depends entirely on how mobile that particular mineral is inside the plant (Figure 12.1). Actively mobile minerals - nitrogen, phosphorus, potassium, magnesium, chlorine, sodium, zinc and molybdenum - can be withdrawn from mature, senescing tissue and translocated through the phloem to actively growing younger leaves whenever supply is short, so a shortage shows up first as chlorosis or necrosis on the oldest leaves, which are effectively sacrificed to keep new growth supplied. Relatively immobile minerals - calcium, sulphur, iron, boron and copper - cannot be withdrawn and relocated once they are deposited in a tissue, often because they are bound into structural components such as cell walls or membranes, so a short …