In this study, we have evaluated the effects of three brown algae (Cystoseira gibraltarica, Bifurcaria bifurcata and Fucus spiralis) as biostimulant on the germination and the growth of pepper (Capsicum. annuum) in vitro as well as in greenhouse. Two different treatments (Amendment/spray) had been tested accordingly, both with varied concentrations ((0.5%, 1% and 2%) for extract and (C1=0.5 g/pot, C2=1 g/pot and C3= 2.5 g/pot) for amendment). The obtained results have shown that the seeds which

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... were treated by C. gibraltarica, and B. bifurcata with a low concentration (0.5%) were slightly germinated with great length of hypocotyls. Similar results have been obtained for the radicle length. On the other hand, the F. spiralis extract improved the percentage of germination, the length of the radical, the hypocotyls, seedling length and dry weight for the three tested concentrations. Also, all concentrations have a favorable effect on seedling biomass. The growth rate in the greenhouse (the root's length, the aerial part length, total length and dry weights) was higher for the plants which received higher concentrations of aqueous extracts of the three species B. bifurcata, F. spiralis and C. gibraltarica. Additionally, the maximum quantity of chlorophyll 'a' has been recorded in the plants treated with B. bifurcata and C. gibraltarica at 2% and F. spiralis extracts at 0.5%. In regards to the protein content, the maximum values were recorded at the level of the plants that were treated with F. spiralis extract at 0.5%. This study has provided important information about B. bifurcata and F. spiralis species could be considered as a good biostimulant to improve pepper's growth.