Moringa leaf extract increases tolerance to salt stress, promotes growth, increases yield, and reduces nitrate concentration in lettuce plants

The use of large amounts of synthetic chemicals in plant cultivation harms the environment and reduces food quality. Therefore, natural alternatives should be used to protect the environment, increase food quality, and decrease food contamination. This study investigated the effect of moringa leaf extract (MLE) as a plant stimulator to enhance growth, yield, and quality of lettuce grown in a saline environment. To examine the effect of application method and extract concentration, this experiment included three levels of seed priming (0, 5 %, and 10 % MLE) and three levels of foliar spray (0, 5 %, and 10 % MLE). MLE application, either by seed priming or foliar spraying, reduced the adverse effects of salt stress and increased lettuce growth, yield, and quality. However, the combined treatment of 5 % seed soaking and 10 % foliar spray showed the best results in increasing antioxidant levels (catalase (CAT), ascorbate peroxidase (APX), and ascorbic acid), relative water content (RWC %), nutrient concentration (N, P, and K), and chlorophyll content, and maintaining membrane integrity by reducing electrolyte leakage (EL %) and sodium accumulation, leading to improved yield parameters (head diameter, head weight, and total yield), and increasing lettuce head quality by reducing nitrate concentration. The results suggest that MLE (5 % seed soaking and 10 % foliar spray) is a practical, effective, and inexpensive approach to alleviate salt stress and improve lettuce yield and quality under saline conditions. However, despite the observed positive effects, further studies are needed to understand the factors determining the response of plants to MLE application.