**3.5 Phosphorus use-efficiency**

Plants can increase their P use-efficiency by adopting various strategies to optimize P-metabolism in the soil. One of the primary strategies is to enhance the uptake of P from the soil, which is achieved by developing an extensive root system that allows plants to explore a larger volume of soil, and the secretion of organic acids and enzymes that solubilize and release bound P in the soil [64]. Plants can increase their P use-efficiency by recycling and reusing internal P reserves. For example, plants can remobilize P from old leaves to new growth areas during leaf senescence, improving their ability to acquire P from the soil [65]. This way the plants recycles and reuses their own internal reserves of P. Plants can remobilize P from old leaves, stems, and other tissues to support new growth, reducing their reliance on external sources of P [66]. This process is especially important under low P availability conditions, where efficiently reallocating P from senescent tissues to new growth can improve plant fitness and productivity [67].
