Effect of seaweed liquid extracts from Ulva lactuca on seedling growth of mung bean (Vigna radiata)

Seaweed extracts contain a variety of compounds, such as macro- and micronutrients and plant growth regulators, which can be used by plants. Such extracts can have both negative and positive effects (depending on the concentration) when directly applied to seeds and plants. The aim of this study was to assess the effects of acid seaweed liquid extracts on growth and biochemical parameters of mung bean (Vigna radiata) under laboratory and greenhouse conditions, using direct applications to seeds and seedlings. Extracts of Ulva lactuca were obtained by hydrolysis with H₂SO₄ at 2, 4, 6, 8 and 10% concentrations. The effects of seaweed extracts with different concentrations, 0.2, 0.4, 0.6, 0.8 and 1.0% were tested on germination parameters (percentage index, mean time, seedling vigour index) and growth parameters (plumule and radicle length, shoot and root length as well as fresh and dry weight) in addition to biochemical parameters (protein content, total chlorophyll, total and reduced sugar) in mung bean. The results suggest that addition of acid extracts at low concentrations (0.2%) can significantly enhance seed germination rates. Higher germination rates were associated with lower mean germination time, high germination index and, consequently, greater seedling vigour and greater plumule, radicle, shoot and root length. In addition, production (fresh and dry weight) of mung bean was significantly higher compared to the control treatments. Biochemical analysis of the seedlings treated with acid seaweed liquid extracts at 0.2% showed higher protein contents. Total chlorophyll concentration of seedlings in all treatments was significantly higher than in the controls plants, whereas the accumulation of total and reducing sugars was highest in treated plants with almost all treatments at higher concentrations.