EFFECT OF METHANOL EXTRACT OF Sargassum virgatum AG (MERT.) – A MARINE BROWN MACROALGA ON SEED GERMINATION AND SEEDLING GROWTH OF SOME AGRICULTURAL CROPS

The allelopathic potential of methanol extract from Sargassum virgatum (Mert.) AG. (Phaeophyta) on the seeds germination and seedlings growth of Lettuce (lactuca sativa), Tomato (Lycopersicon esculentum), and barley (Hordeum vulgare) was conducted. Methanol extracts from S. virgatum at concentrations 25, 50, 100, and 200 ppm were applied under laboratory conditions. Tomato, lettuce and barley germination were stimulated by 25 and 50 ppm of methanol extract and tomato recorded the highest percentage of germination. The plumule and radicle growth was reported to be greatly stimulated at low concentrations, meanwhile, the high concentrations especially, 200 ppm, recorded slight inhibition effects compared with control. Moreover, roots appeared to be more sensitive to allelopathic effects than shoots. In HPLC analysis, the data indicated the presence of seven free phenolic compounds among which vanillic and Ferulic acids were the most abundant. Upon the present results, methanol extract had stimulatory allelopathic potential at low concentrations and accordingly it could be used as a biofertilizer for lettuce, tomato and barley. INTRODUCTION Harmful algal blooms have increased worldwide over coastal graces (Anderson, 1989; Hallegraeff, 1993; Van Dolah, 2000) due to their physiological characteristics such as their rapid nutrient uptake, high growth rate and broad environmental tolerance (Smayda, 1997; Taylor et al., 2001). Decomposed algal biomass causes oxygen depletion in the water column (mostly in the bottom waters), as well as, devastating consequences to the benthic community (Allen et al., 2006). Besides, some of these bloom-forming species have negative allelopathic actions on the growth of the other organisms through the production and releasing of secondary metabolites (Graneli and Hansen, 2006). Brown algae are very important members of many marine communities and often dominate these communities in terms of structure and biomass, particularly in temperate and polar waters (Amsler and Fairhead, 2006). Brown algae, such as Sargassum, are rich with many natural products (Segawa and Shirahama 1987, Hay and Fenical 1988, Hay 1996, Pereira and Yoneshigue-Valentin 1999). The most important identified natural products in brown algae were phenolic compounds. (Yoshie, et al, 2000, Santoso, et al., 2002, Yoshie-Stark, et al, 2003). Additionally, many studies stated that phenolic compounds have been known to be involved in allelopathic phenomenon (Inderjit, 2002, Chon et al, 2005). The production of phenolic compounds in (1) Hamada Ragab Ghereib, Lecturer at Department of Botany, Faculty of Science, Beni-Sueif University. Address: Salah Salm Street, Beni-Sueif, Egypt. E-mail : [email protected] Mobile: ++20186688860 Fax: +2082-2334-551 Thalassas, 2010, 26 (1): 13-21 An International Journal of Marine Sciences