PHOSPHORUS UPTAKE AND TRANSPORT MECHANISM IN PLANTS

Phosphorus (P) is an indispensable macronutrient required for plant growth, development, energy transfer, photosynthesis, respiration, nucleic acid synthesis, and membrane formation. Although agricultural soils often contain substantial quantities of phosphorus, only a small fraction is available for plant uptake because it is predominantly present in insoluble or fixed forms. This limited bioavailability significantly restricts crop productivity and results in low phosphorus use efficiency, necessitating excessive fertilizer application with adverse environmental consequences. This review highlights the major mechanisms of phosphorus mobilization in the rhizosphere and the molecular basis of phosphorus uptake through specialized phosphate transporters. Plants enhance phosphorus availability by secreting organic acids, extruding protons, releasing phosphatases and phytases, modifying root architecture, and establishing symbiotic associations with arbuscular mycorrhizal fungi and phosphate-solubilizing microorganisms. Phosphorus is absorbed mainly as orthophosphate ions (H›PO, and HPO,) through the phosphate transporter (PHT) family, particularly the high-affinity PHT1 transporters that mediate uptake under phosphorus-deficient conditions. Other transporter families, including PHT2, PHT3, PHT4, and PHT5, regulate intracellular phosphate distribution, organellar transport, vacuolar storage, and remobilization to maintain phosphorus homeostasis. The review also discusses the molecular regulation of phosphorus acquisition through phosphate starvation response pathways involving PHR1 transcription factors, miR399, SPX proteins, and plant hormones. Furthermore, it emphasizes the importance of beneficial microorganisms, integrated nutrient management, phosphorus recycling, and advanced biotechnological approaches such as molecular breeding and genome editing to improve phosphorus use efficiency. A comprehensive understanding of phosphorus mobilization and transport mechanisms is essential for developing sustainable crop production systems that enhance nutrient use efficiency, conserve finite phosphorus resources, and ensure long-term global food security.