Moringa leaf extract biostimulant in modulating proline of rice seedlings in drought: Integration of phytochemical screening and physiological assessment

Drought stress is one of the main factors limiting rice plant growth, especially during the seedling stage. Water deficiency causes physiological disturbances, characterized by decreased photosynthetic activity and increased oxidative stress. The use of natural-based biostimulants is a strategic alternative to increase plant tolerance to these conditions. This study aims to determine the metabolite profile of moringa leaf extract and to evaluate its biostimulant effects on proline and chlorophyll levels and on rice seedling growth under varying levels of drought stress, while correlating the extract's phytochemical content with the plant's physiological responses. The metabolite profiling was obtained through GC-MS analysis. At the same time, the field study was conducted using a factorial Completely Randomized Block Design (CRBD) with two factors, namely moringa leaf extract concentration (0%, 5%, 10%, and 15%) and drought stress level (100%, 60%, and 30% of field capacity). Agronomic parameters included plant height and root length, while physiological parameters were assessed by measuring chlorophyll and proline content. The results showed that moringa leaf extract contains various metabolites with the potential to act as biostimulants to increase plant tolerance to stress, including vitamin E, n-hexadecanoic acid, octadecatrienoic acid, pentatriacontene, and β-sitosterol. Application of 5% moringa leaf extract increased plant height, while 15% concentration increased root length under stress conditions. Relative chlorophyll a content increased with increasing stress, and higher Moringa Leaf Extract (MLE) concentration increased chlorophyll content under moderate stress (60% Field Capacity(FC)). MLE application increased proline content only under moderate stress (60% FC). These findings indicate that moringa leaf extract has potential as a natural biostimulant to enhance rice seedling tolerance to drought stress.