Algal biostimulants as climate smart solutions for enhancing abiotic stress tolerance in crops

Abstract

Climate change causes abiotic stresses like drought, salinity, temperature extremes and heavy metal contamination. These stresses threaten global agricultural productivity and food security. Chemical-based inputs may improve short-term yields, but they often harm soil health and increase environmental problems. In this situation, algal biostimulants from macroalgae, microalgae and cyanobacteria have emerged sustainable solutions for improving crop resilience to these stresses. These bioformulations are rich in polysaccharides, phytohormones, betaines, amino acids, phenolics, carotenoids and essential minerals. Together, they help plants respond better under stress. Algal biostimulants boost photosynthetic efficiency, strengthen antioxidant defences, regulate osmolyte accumulation and maintain ionic balance, which reduces oxidative damage and preserves cell integrity. They also enhance root structure, improve nutrient uptake and increase water use efficiency, supporting plant growth in extreme conditions. Recent evidence shows that they assist in priming stress-responsive genes, stabilise hormonal signalling and enhance stress memory for better adaptation. Furthermore, algal formulations improve soil health, boost microbial activity and reduce reliance on synthetic fertilisers, fitting into climate-resilient agricultural practices. Despite their several advantages, challenges remain in standardisation, dosage optimisation, understanding mechanisms and validating large-scale field applications. This review summarises existing knowledge on the mechanisms, formulations and specific applications of algal biostimulants. It emphasises their potential as eco-friendly solutions for improving tolerance to abiotic stress and fostering sustainable crop production in a changing climate.