Physiological studies on the Influence of Selected Algal Extracts on the Growth of Eruca sativa Based on Different Methods of Treatment

Seaweed represents a promising biological resource for use as a biofertilizer. This study was conducted in Umluj, Saudi Arabia, with three macroalgal species Galaxaura oblongata (Tricleocarpa fragilis, Rhodophyta/red algae), Sargassum latifolium (Phaeophyta/brown algae), and Turbinaria ornata (Phaeophyta/brown algae) were harvested from the Red Sea coast. Algal treatments were applied via three methods: (1) soil mixing with dry algae, (2) seed soaking, and (3) foliar spray, using aqueous extracts at two different concentrations of 1.5 and 2.5 ppm. The result showed that the aqueous seaweed extracts of the three examined seaweeds (G. oblongata, T. ornata, and S. latifolium) are rich in soluble sugars, phenols, and flavonoids, with T. ornata exhibiting the highest total antioxidant capacity. Treatments significantly affected Eruca sativa in terms of seedling length, biomass, photosynthetic pigments, protein content, total soluble sugars, phenols, flavonoids, antioxidant enzymes, and nutrient uptake. Seed soaking with T. ornata extract at 2.5 ppm yielded the most pronounced effects, followed by foliar spray and soil mixing. These findings underscore the potential of red and brown seaweeds as biofertilizers.