The potential of beach wrack as plant biostimulant to mitigate metal toxicity: mineral composition, antioxidant properties and effects against Cu-induced stress

• Published in: Journal of applied phycology 2022-02, Vol.34 (1), p.667-678
• Main Authors: Sousa, Filipa, Martins, Maria, Sousa, Bruno, Soares, Cristiano, Azenha, Manuel, Pereira, Ruth, Fidalgo, Fernanda
• Format: Article
• Language: English
• Subjects: Abiotic stress; Agrochemicals; Algae; Amino acids; Antioxidant properties; Antioxidants; Barley; Beaches; Biomedical and Life Sciences; Biostimulants; Circular economy; Climate change; Composition effects; Copper; Dietary minerals; Dry matter; Ecology; Flavonoids; Freshwater & Marine Ecology; Hordeum vulgare; Lead; Leaves; Life Sciences; Metabolites; Metals; Micronutrients; Mineral composition; Mitigation; Nutrients; Organic fertilizers; Phenols; Photosynthesis; Photosynthetic pigments; Phytotoxicity; Pigments; Plant extracts; Plant Physiology; Plant Sciences; Residues; Seaweeds; Seedlings; Sugar; Sustainability; Toxicity
• ISSN: 0921-8971; 1573-5176
• DOI: 10.1007/s10811-021-02636-4

Plant biostimulants such as seaweed extracts, present a sustainable alternative to agrochemicals. Moreover, the accumulation of beach-cast seaweed (wrack), due to climate change and anthropic pressures, is expected to increase in the coming decades. Thus, from a perspective of circular economy, based on the valorisation of an organic residue, this study aimed at achieving an elemental and biochemical characterisation of beach wrack and understanding the effects of an aqueous extract prepared from this residue on the mitigation of metal-induced stress, using barley ( Hordeum vulgare L.) as a model. The quantification of wrack’s macro- and micronutrients showed that K, Ca and Na were the most abundant elements, being this composition similar to that of other organic fertilisers. Furthermore, despite the studied wrack having lower values of photosynthetic pigments, amino acids and sugars, higher amounts of phenols and flavonoids (8.35 ± 0.24 and 3.95 ± 1.22 mg g −1 dry matter respectively) were detected when compared to freshly collected seaweeds. This work highlighted that wrack showed potential as a fertiliser—through increasing root biomass (63%) and leaf biometry (up to 45%) in plants treated with 5.0 and 7.5 g L −1 wrack extract alone—also being a possible cost-effective, eco-friendly and sustainable biostimulant to mitigate the phytotoxic effects of Cu, since plants treated with 7.5 g wrack L −1 showed an increase of 34% in leaf length, when compared to seedlings exposed only to Cu.