Seaweed Marine Algae: Nutritional Values and Plant Growth Regulators for Sustainable Agriculture

In earlier days, usages of these marine aquatic plants otherwise called weeds (Marine algae) were not understood well. Hence the name was given to these marine plants weeds as “Seaweeds”. Seaweeds also known as macroalgae are primitive non-flowering plants without true root, stem and leaves. Marine algae are aquatic plants belonging to the kingdom Thallophyta and considered an essential part of the marine ecosystem that inhabits the coastal regions. Seaweeds occur in the intertidal, shallow and deep waters of the sea up to 180m depth and also in estuaries and backwaters. They grow on rocks, dead corals, stones, pebbles, solid substrata and on other plants. Macroalgae have been estimated at 9000 species and mainly categorized into three groups. There are three main groups; green, brown and red of macroalgae based on the presence of photosynthetic pigment. Approximately 221 seaweeds species (Red Algae Rhodophytes 125, Brown Algae Phaeophytes 64 and Green Algae Chlorophytes 32) are using for commercial development worldwide, and out of 145 species are utilized as food, traditional medicines 24 species, almost 25 species in agriculture, including animal feed and compost. Marine algae source for the production of phytochemicals such as agar, carrageenan and algin. The luxuriant growth of seaweeds is found in southeast of Tamil Nadu, Gujarat Coast, Lakshadweep and Andaman-Nicobar Islands. Rich seaweed beds occur at Mumbai, Ratnagiri, Goa, Karwar, Varkala, Vizhituam, Pulicat Lake and Chilka Lake.

Seaweed extract is a new generation of natural organic fertilizer containing highly effective nutrients. The brown algae are the most commonly used seaweed in agriculture. Seaweed extracts contain different phytohormones like; Auxins, Gibberellins, Cytokinins, Abscisic acid, Ethylene, Betaine and Polyamines and other growth promoters along with trace elements and minerals, protein, amino acids, iodine, bromine, antibiotics, vitamins and many bioactive substances to promotes growth and yield as well as enhance the resistant ability of many crop from biotic and abiotic stress, which enhance the yield and yield attributes of crops when applied exogenously. Unlike chemical fertilizers, extract derived from seaweeds are biodegradable, non-toxic, non-polluting and non-hazardous to humans, animal and birds (Dhargalkar et al., 2005). Seaweeds and various seaweed extracts have been utilized in agricultural practices since long. Sustainable agriculture is the successful management of resources for agriculture to satisfy changing human needs while maintaining or enhancing the quality of the environment and conserving natural resources (CGIAR, 1978). Seaweeds and seaweed extracts which are important components of organic farming are a promising avenue for yield maximization through their biostimulatory role on crop plants. Seaweeds and their extracts are integral to sustainable farming because of their multifarious utility in various fields of agriculture including nutrient and crop management, growth promotion and plant protection etc.