Growth and physiological responses of wheat plants to polyphosphate and orthophosphate fertilizers supply under salt stress

Phosphorus (P) availability is significantly reduced under salt-stress conditions. Appropriate P fertilization can effectively alleviate its negative impact on plant growth and development. This study examines the impact of two P fertilizer forms (Ortho-B and Poly-B) on durum wheat tolerance to salinity (S1 = 3 dS m⁻¹ and S2 = 6 dS m⁻¹) under hydroponic conditions. A completely randomized design with six treatments and five replicates per treatment was used. At S2 salinity level, Poly-B outperformed Ortho-B (p < 0.05) by increasing shoot and root dry weights by 867 % and 127 %, respectively. It also improved root morphology (length, surface area, and crossings) by up to 353 %, enhanced chlorophyll content by 41 %, and raised shoot phosphorus content by 20 %, indicating superior stress resilience. These findings suggest that polyphosphate fertilizers are more effective in mitigating salt stress effects in wheat. Future long-term field studies are recommended to confirm these results and assess their agronomic applicability at scale.