Effects of Individual and Combined Applications of Seaweed Extracts and Plant Growth-Promoting Rhizobacteria (PGPR) on Plant Growth and Physio-Biochemical Properties of Soft Wheat and Faba Bean

Abstract

ABSTRACT The research on carbon materials and plants primarily focuses on their use in soil, showing variable effects. However, significant gaps exist regarding their impact under stress conditions (such as drought, salinity, etc.) and their interactions with plant physiological processes. Long-term effects on plant health and ecosystems are understudied, as are their interactions with other biofertilizers like algae extracts and plant growth-promoting rhizobacteria (PGPR). The aim of the present study was to evaluate the effects of seaweed extracts and PGPR on plant growth and some physio-biochemical properties of soft wheat (Triticum aestivum L.) and faba bean (Vicia faba L.). Two concentrations of aqueous extract from two seaweeds, Fucus spiralis (F) and Ulva rigida (U), and the PGPR bacillus strain solution S48 (S48S) were used either individually or in combination. All treatments were applied as foliar sprays. The findings showed that the combined application of Fucus spiralis extract [25%] (F), Ulva rigida extract [50%] (U), along with the PGPR S48 bacillus strain solution (S48S) promoted plant growth (50.93 cm for faba bean) and root development (17.90 cm for wheat). This treatment also resulted in increased chlorophyll content (3.25 mg/g Fresh Weight (FW) in soft wheat and 3.93 mg/g FW in faba bean), proteins (14.66 µg/mg FW in soft wheat and 23.79 µg/mg FW in faba bean), amino acids (0.46 mg/g FW in soft wheat and 0.56 mg/g FW in faba bean), and total carbohydrates (529.8 µg/ml in soft wheat and 340.7 µg/ml in faba bean) as compared to controls. On the other hand, the nitrate reductase activity was enhanced by seaweed extract application in both crops. Phosphorus (P) uptake by soft wheat and faba bean was significantly improved following the application of Ulva rigida extract [50%] (U), the PGPR S48 bacillus strain solution (S48S), and the co-treatment of Fucus spiralis extract [25%] (F) with the PGPR S48 bacillus strain solution (S48S). The findings suggest that the combined application of Fucus spiralis extract (F) and Ulva rigida extract (U) with the PGPR S48 bacillus strain solution (S48S) can significantly improve plant growth and nutrient absorption in durum wheat and faba bean. This offers a sustainable alternative to chemical fertilizers, reducing pollution and promoting healthier ecosystems. Furthermore, these biological treatments enhance plant resilience to abiotic stresses, potentially increasing yields in challenging conditions. By reducing reliance on chemical fertilizers, these practices can save money for farmers and advance sustainable agriculture.