Bioactivity of Ulva lactuca L. acetone extract on germination and growth of lettuce and tomato plants

Abstract

Ethanol, butanol and acetone extracts of

Ulva lactuca L. (Chlorophyta) at concentrations 10, 30, 100 and 300 ppm for each were applied to determine their biological activity under laboratory conditions using etiolated wheat's coleoptile growth bioassay. Acetone extract was the most active one and was selected to investigate the allelopathic potential on lettuce and tomato's seed germination and seedling growth. Nine free phenolic compounds were detected in the Ulva acetone extract by using HPLC analysis. Vanillin and p- coumaric acid was recorded as the abundant compounds while ferulic acid and salicylic acid existed in less amounts. Compared with the control, the germination of lettuce and tomato were stimulated by 5.8 and 21.5%, respectively, when treated with low concentration of acetone (30 ppm). In contrast, high concentration (300 ppm) retarded the germination and recorded high inhibition effect on lettuce (44.6%). Acetone extract, at 30 ppm, stimulated the radicle and plumule growth of lettuce by 10.6 and 27%, respectively, and tomato by 22.5 and 35%, respectively. Meanwhile, at 300 ppm, radicle and plumule growth of lettuce was greatly inhibited by 40.6 and 30%, respectively, whereas tomato was  slightly inhibited. Moreover, roots appeared more sensitive to allelopathic effect than shoots.