Seaweed Extract Biostimulants Differentially act in Mitigating Drought Stress on Faba Bean ( Vicia faba L. )

Prolonged drought periods cause a cascade of biochemical alterations in plants and lead to reduction in plant growth and crop productivity. Seaweed extracts are a category of plant biostimulants that are effective in alleviating drought stress on plants. However, the effect of seaweed extracts on attenuating the negative impact of drought on Faba bean ( Vicia faba L .) under arid and semi-arid conditions has received little attention. This study was conducted to evaluate the performances of extracts made from Fucus spiralis (FSE), Ulva lactuca (ULE), Laminaria ochroleuca (LOE), and Ascophyllum nodosum (ANE) in mitigating drought stress in Faba bean. The biochemical profile of the extracts was characterized, and key physiological and biochemical parameters of Faba bean plants were assessed during both drought and recovery phases. All investigated extracts positively affected plant biomass under drought stress conditions. Plants that received LOE had a higher relative water content and lower malondialdehyde concentration in comparison with stressed control plants. The positive effect of ANE and FSE was mainly attributed to proline accumulation in plant tissues under stress. FSE and ULE application resulted in a higher concentration of soluble sugars in treated plants in comparison to the control plants. It was concluded that seaweed extracts originating from different sources and extracted using different protocols act differentially in altering plant-related stress traits. Overall, seaweed extracts are potentially an effective solution to manage the negative impact of water scarcity on Faba bean.