Phosphorous

Phosphorus is another highly mobile nutrient in plants, and is needed for healthy plant tissue growth. Deficiencies of phosphorus can be noticed in older leaves first. Signs include stunted growth, and a red color due to elevated anthocyanin pigments. Excess phosphorus can prevent plants from absorbing zinc, iron, and copper into the roots, leading to deficiencies in those micro-nutrients. Testing a comparison between old growth sap and new growth sap can show trends in phosphorus movement.