ABSTRACT
This chapter discusses the seaweed extracts as source of plant nutrients and plant growth regulators. Seaweeds include the macro-algae found in the intertidal zones of marine ecosystems around the world. Seaweeds are reported to have plant-growth promoting activity and have been utilized around the world as organic manures and fertilizers in agriculture and horticulture. 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. Several species of marine algae are being utilized for preparation of seaweed liquid fertilizers. Seaweed extracts affect various aspects of germination, growth, physiology and development including overall health of the plants. The effect of seaweed extracts on crop plants can be discussed on the aspects like germination; root development and mineral absorption; shoot growth and photosynthesis; crop yield and vegetative propagation. The seaweeds are not only a source of bio-fertilizers but also bio-stimulatory substances including phytohormones.
