Application of nitric oxide donor improves the response of Khaya grandifoliola C. DC seedlings to water deficit

The cultivation of Khaya grandifoliola has expanded in tropical regions, as a promising option for high-quality timber production. However, water deficit caused by prolonged drought can lead to seedling mortality and reduced biomass accumulation. Nitric oxide (NO) has been reported to play a role in plant responses to abiotic stress, including drought. This study aimed to evaluate the potential of NO to mitigate the effects of water deficit on the physiological performance of K. grandifoliola seedlings. Plants were treated with NO donor S-nitroso-mercaptosuccinic acid (MSNO) applied to the substrate at concentrations of 0, 0.1, 0.2, and 0.4 mM. Water deficit was imposed by interrupting irrigation for 22 days. Each treatment consisted of 15 replicates. The application of 0.2 mM MSNO improved leaf gas exchange, resulting in higher net photosynthesis, transpiration, stomatal conductance, and water use efficiency compared to plants under water deficit. In addition, MSNO-treated plants showed higher relative water content, lower proline accumulation, and reduced mortality. These results suggest that MSNO application enhances drought tolerance in K. grandifoliola seedlings, representing a potential strategy for improving seedling establishment under water-limited conditions.