Potential of Foliar Application of Seaweed Extracts as a Biostimulant for Abiotic Stress Alleviation on Crop Production

Abstract

Abiotic stress is one of the major perils in agriculture that reduces crop yield at an alarming rate. Hence, exploring an important plant stress-mitigating technique is critical. Seaweeds are extensively used as plant biostimulants and their biostimulatory properties are due to bioactive compounds such as polysaccharides, pigments, phenolic compounds, proteins, phytohormones, and numerous micro and macro nutrients. Foliar applications of seaweed extracts (SWEs) exhibit promising outcomes for plants’ stress alleviation. Seaweed, namely Ascophyllum spp., Sargassum spp., Kappaphycus spp., and Ulva spp. are the best candidates evaluated to improve plant growth and development under various abiotic stress conditions. Foliar sprays of SWEs improve crop growth, boost final yield, and product quality. Furthermore, the mechanisms activated in response to stress when SWEs are used are largely unknown. However, existing phytostimulatory components could affect plant metabolism by activating numerous enzymes in the phenylpropanoid pathway, and their antioxidant properties could lessen the degenerative effects of reactive oxygen species that accumulate in plant tissues during a stressful environment. Noticeably, SWEs regulate the expression of phytohormone-responsive genes, which in turn control endogenous phytohormone levels, thereby improving plant growth and development. This review explores seaweed taxonomy, biostimulatory properties, and the impact of foliar applications of SWEs on crop production under abiotic stresses, including the way SWEs attenuate the deleterious effect, highlighting limitations, areas requiring further investigation, and potential developments.