Seaweed and Associated Products: Natural Biostimulant for Improvement of Plant Health

Seaweeds are macroalgae fit into the class Phyophyceae and best known as brown algae. They are mainly composed of polysaccharides such as laminarin, fucoidan, and alginates. Several products based on seaweeds are known to be useful for humans and plants. Extracts obtained from seaweeds contain several bioactive compounds. Such bioactive compounds induce resistance in plants against different biotic and abiotic stresses. Seaweed extracts can also contain countless plant-bioactive inorganic and organic compounds such as mannitol, polysaccharides, oligosaccharides, phytohormones (auxins, cytokinins, gibberellins, betaine), antioxidants, and vitamins. It also contains a low concentration of minerals (calcium, boron, zinc, potassium, phosphorus, magnesium, and several other trace elements). Seaweed extract can stimulate plant growth and enhance the rate of photosynthesis. Seaweed extracts boosted rates of seed germination, crop growth, yields, and shelf life of produce in post-harvest conditions. It can reduce the effect of diseases due to fungal, viral, and bacterial pathogens. The present chapter describes the impact of seaweed and their products in the agricultural system.