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.