The use of biostimulants in agriculture has shown fabulous potential in combating climate change induced stresses such as drought. Improving agricultural productivity requires sustainable drought stress management. This study investigates the potential of Musa paradisiaca L. (banana) and Opuntia ficus-indica (L.) Mill. (prickly pear) peels as natural biostimulants to alleviate drought stress in Vicia faba L. (faba bean). A greenhouse experiment was conducted using peel powder treatments (5 g/pot) under different field capacity levels to evaluate germination parameters, plant biomass and water content. Leaf ultrastructure and stress-related gene expression were also evaluated. In addition, the physicochemical characterization of peel powders, including soluble protein, soluble sugars, total phenolics and flavonoids, was performed. The physicochemical characterization of banana and prickly pear peel powders revealed the presence of considerable amounts of phenolics, flavonoids, sugars, and proteins, with higher phenolic and flavonoid contents detected in Musa paradisiaca peel powder. The application of both peel extracts, particularly Musa paradisiaca L., significantly improved shoot and root length, plant biomass, and water content compared to untreated control plants. Under representative drought stress, most growth parameters and water content of the studied plants were higher in Musa paradisiaca L.-treated plants compared to their respective control, whereas Opuntia ficus-indica (L.) Mill. treatment showed comparatively lower values. TEM observations revealed improved leaf ultrastructure in treated plants under drought conditions. While qRT-PCR analysis indicated upregulation of stress-related genes. The transcript level of ascorbate peroxidase was significantly higher in plant treated with Musa paradisiaca L. than in plant treated with Opuntia ficus-indica (L.) Mill. when exposed to moderate drought (40%FC), suggesting a potential involvement of APX in antioxidant-related stress responses under drought conditions. These results suggest that natural peel powders could be a viable strategy for promoting sustainable agriculture and improving plant performance under drought. Overall, modulation of stress-related gene expression may contribute to improved drought responses in faba bean. These effects appear to be associated with improved water status, preservation of cellular ultrastructure, and regulation of stress-responsive pathways.
Megahed et al. (Tue,) studied this question.