Temporal Phosphorus Allocation and Resorption Plasticity Drive Interspecific Phosphorus‐Use Efficiency in Rice‐Rapeseed Rotations

Diversified cropping rotations combining species with contrasting phosphorus (P) use strategies can improve yields and sustainability, yet the physiological basis for interspecific differences in internal P-use efficiency (PUE) remain elusive. We investigated species-specific temporal dynamics of leaf P allocation plasticity, resorption capacity, and their coordination with lipid metabolism and photosynthesis in a rice (Oryza sativa L.)-rapeseed (Brassica napus L.) rotation. Rice exhibited higher PUE and P resorption efficiency than rapeseed, associated with its greater and progressively increasing allocation to inorganic-P (Pi) during expansion, and prolonged P remobilisation spanning over half of the leaf lifespan. This extended remobilisation was enabled by efficient Pi export and coordinated degradation of lipid-P and nucleic acid-P. In contrast, rapeseed minimised lipid-P investment to sustain Pi and metabolic-P above photosynthetic thresholds and confined P resorption to a short senescence phase (c. 12.5% of lifespan). Under P deficiency, rapeseed enhanced phospholipids replacement and accelerated P resorbed from nucleic acid and metabolic-P pools, while rice maintained high P resorption via simultaneous degradation of phospholipids and nucleic acids. These findings demonstrate that a higher inorganic/organic P ratio and prolonged internal P recycling underlie enhanced PUE, offering insights into optimising crop selection and precision P management in sustainable cropping systems.