An in-depth review on the mechanistic insights of marine macroalgal compounds in enhancing plant tolerance to stress induced by saline soil conditions

Abstract

Plants have developed many defensive mechanisms to maintain their metabolism and growth under stress that, albeit inadequate with increased soil salinization rates and climate change, deliberately affect plant growth, productivity, and quality. As an alternative, yet effective, economical, and sustainable choice of environmentally benign source, seaweeds are proving to be potential replacements for conventional plant protectants and biostimulants. Seaweed extracts from various families have known to exert ameliorating effect in plants affected by salt stress as a cumulative action of sequential bio array of compounds under diverse categories such as phytohormones (Auxin, cytokinin, and Gibberilic acid), polyamines (putrescine and spermidine), phenolics (Vanillic and gallic acid), protein (Taurine, phosphoserine), carbohydrates (Trehalose, sorbitol, and mannitol) and betaines (glycine and proline beatine, and glycine, aminobutyric acid). These compounds are sought to promote the production and accretion of ameliorative compounds such as osmolytes that activates the MAPK pathway, triggering various signal cascades activating several genes and miRNAs that promote Na+ compartmentalization, Cl− efflux, increase cytosolic Ca+, ion homeostasis, cell–organ integrity. An increased rate of antioxidant enzymes (peroxidase, superoxide dismutase, and ascorbate peroxidase) in rapidly scavenging reactive oxygen species is also observed. Consequently, there is an increase in chlorophyll activities promoting sugar allocation, water, and resource utilization efficiencies, thereby protecting and promoting plant growth and productivity in an eco-friendly yet effective manner.

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