Biostimulant Potential of Seaweed Extracts Derived from Laminaria and Ascophyllum nodosum

Abstract

Brown seaweeds belonging to the genus Laminaria or Ascophyllum are used in traditional and modern agriculture. They are an alternative way to the application of chemical pesticides or synthetic fertilizers frequently required to improve the agricultural production. Macroalgae extracts are used in many countries (India, China, France, Ireland) to improve the crop yield. Seaweed extracts from Ascophyllum nodosum and Laminaria have often been described to produce positive effect on the germination of seeds and morphological development of plants with an agronomic interest. The main effects are observed especially on the plant growth and root elongation. The presence of growth hormones such as auxins or auxin-like compounds in the seaweed extracts mainly explains these stimulation mechanisms. The positive effect of brown seaweed extract application on fruit quality is also well documented. In regard to these agronomic properties, seaweed extracts are also recommended to limit the biotic and abiotic stresses. The scientific literature gives some information on the bioactive compounds involved in these mechanisms of plant tolerance to these two types of stresses. Some algal polysaccharides, such as laminarin, are well known to induce the defense mechanisms of plants. These phytoelicitors are often used by foliar spraying. The goal of this chapter is to highlight the recent advances in the use of seaweed extracts as agronomic biostimulants. It also describes the main compounds involved in the stimulating activity.