Tolerance To Low Phosphorus Was Enhanced By An Alternate Wetting And Drying Regime In Rice

Phosphorus (P) deficiency is a limiting factor for sustainable rice (Oryza sativa L.) production. However, little is known about how rice varieties that differ in tolerance to low P perform under water-saving irrigation. In this study, we characterized the responses of two rice varieties, ZD88 that has a weak tolerance to low soil P and YJ2 that has a strong tolerance to low soil P to two irrigation regimes under both optimal P (NP, 46.9 mg/kg Olsen-P) and low P (LP, 6.8 mg/kg Olsen-P). The first irrigation regime involved continuous flooding (CF), while the second involved alternate wetting and moderate soil drying (AWD). The study was conducted in plants grown in pot over two years. YJ2 exhibited stronger tolerance to LP than ZD88 under both irrigation regimes. Compared to CF, plants grown with AWD produced higher grain yields and had increased phosphorus translocation efficiencies, as well as higher metabolic phosphorus efficiencies and increased phosphorus harvest index values. The water use efficiencies of the two rice varieties were increased under both NP and LP under AWD conditions. The AWD regime also resulted in higher shoot dry weights and increased photosynthesis rates under LP compared with CF. Moreover, the remobilization of non-structural carbohydrates from stems to the grain was also increased under the AWD regime, together with higher activities of sucrose-phosphate synthase, sucrose synthase and peroxidases and increased abscisic acid contents in grains. Root dry weights and root to shoot ratios were also increased under AWD conditions, together with increased root acid phosphatase activities. Taken together, these results demonstrate that the AWD regime benefits rice production under LP environment.