Seaweeds

Seaweed extracts are the new type of products currently used in plant cultivation. The sources of seaweed extracts are different species of marine algae which seem to be valuable and not wholly discovered biological material [1].

For ages, extracts obtained from algae have been used as feed additives for animals nutrition improvement [2]. Furthermore, they have been used as industrial raw material or in production of natural cosmetics. Nowadays, seaweeds and products obtained from marine algae constitute the subject of interest in agriculture with emphasis on its application in sustainable agriculture [1]. Marine algae are classified by the researchers as the most important group of organisms which can be widely used in plants nutrition.

Biologically active compounds

Seaweed extracts act as biostimulants mainly due to the presence of plant hormones [3]. Main phytohormones identified in seaweed extracts are: auxins, cytokinins, gibberelins, abscisic acid and ethylene [3,4]. Auxins are responsible for elongational growth of plant tissues and apical dominance, cell division, plant movements and plant aging [3, 5, 6]. Cytokinins are involved in cell division regulation affecting plant growth and rest period. Moreover, they inhibit aging of plant tissues and play crucial role in transport of nutrients [3,6]. One of the basic functions of gibberellins are initiation of seed germination, growth regulation, braking bud dormancy, florescence and fruits development [3, 5, 6]. Abscisic acid and ethylene are responsible for response to stress factors, inhibition of cell growth, acceleration of plant aging [3, 5, 6]. Furthermore, abscisic acid participates in regulation of seed germination. Seaweeds the most widely used in agriculture due to their good biostimulant activity are red algae: Corralina mediterranea, Jania rubens, Pterocladia pinnata, green algae: Cladophora dalmatica, Enteromorpha intestinalis, Ulva lactuca and brown algae: Ascophyllum nodosum, Ecklonia maxima, Saragassum spp [7].

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