Post-anthesis Roots Metabolic Activities Relate Low Phosphorus (P)-Tolerance in Rice (Oryza sativa L.)

Post-anthesis effect of phosphorus (P)-deficit is less studied in plants. P-deficit analysis is rarely performed in different tissues of the plant together. The present study analyzed total-P, inorganic-P, acid phosphatases, ribonucleases, carbohydrates, and antioxidants in the roots, lower leaves, flag leaves, and spikelets at 0, 10, 20, and 30 days after anthesis and recorded yield components at harvest in rice cultivars CSR10 (low-P tolerant) and Pusa44 (low-P susceptible) under P-deprivation (P-0) compared to P-application at 30 kg ha(-1) (P-30). Total-P was deficient in the roots and leaves of Pusa44 compared to CSR10 under P-0. Acid phosphatases and ribonucleases were enhanced by roots under P-0, and the increase was exceptionally high in CSR10. Hexoses, sucrose, and starch levels remained low in the vegetative tissues of Pusa44 compared to CSR10 under P-0. Starch and sucrose were mobilized from vegetative tissues especially from the roots of CSR10 compared to Pusa44 under P-0. Sucrose and starch levels were high in the spikelets of CSR10 compared to Pusa44 under P-0. Antioxidants were high in the vegetative tissues especially in the roots of CSR10 compared to Pusa44 under P-0. At harvest, unfilled grains per panicle increased and grain yield reduced in Pusa44 under P-0. Results concluded that post-anthesis roots metabolic activities, in the form of acid phosphatases/ribonucleases for P-acquisition and antioxidants to counteract stress and starch/sucrose mobilization toward spikelets, may play an important role toward low-P tolerance in rice.