Exogenous application of proline and phosphorus help improving maize performance under salt stress

Salinity is one of the important abiotic stresses that challenge crop productivity worldwide. Crop nutrition management and exogenous application of proline may help improve plant salt tolerance. This study investigated the effects of exogenous proline (100 mM) and phosphorus (P; 10 and 100 mg kg⁻¹ sand) application on the growth, P content and ionic balance in maize under salt stress. Seedlings of a maize hybrid 30Y87 were grown in sand-filled pots maintained under normal (1 dS m⁻¹) and salt stress conditions (6 dS m⁻¹). Salt stress caused a significant reduction in plant photosynthetic efficiency, plant growth, and shoot and root P contents and tissue potassium (K⁺) contents whereas a significant increase in tissue sodium (Na⁺) and chloride (Cl⁻) was also noted. However, the application of proline and P ameliorated the impact of salt stress by restricting the Na⁺ and Cl⁻ uptake and accumulation, and significantly improved plant light absorption capacity, plant growth, P contents and tissue K⁺ contents under both control and salt stress conditions. In this regard, the application of proline with a high rate of P nutrition was more effective. In conclusion, co-application of proline with a high rate of P nutrition synergistically restricted the Na⁺ and Cl⁻ accumulation and improved the plant growth under salt stress.