Evaluation of biostimulant and salt-mediated stress alleviating activities of tropical red and brown seaweeds based biostimulant through green gram seedling cut assay technique

Crop yield and quality improvements, building of resistance toward biotic and abiotic stresses and enhancing nutrient use efficiency are some of the demonstrated benefits of seaweed extracts when they applied on the crops. In the present study, a concentrated seaweed extract (CSW) was produced by a blend of red (<i>Gracilaria salicornia</i>) and brown seaweed (<i>Sargassum swartzii</i>) extracts and evaluated its biostimulant and salt mediated stress alleviating activities by using a green gram (<i>Vigna radiata</i>) seedling method. The CSW (soluble solids: 29.93 ± 0.84%) was tested to contain macro- and micronutrients, plant growth regulators (auxins, cytokinins, and gibberellic acid), amino acids, and alginic acids. The biostimulant activity was evaluated by growing the stem cuttings of green gram seedlings in different concentration of CSW for 10 days and roots developed were measured by a WinRhizo Pro root imaging system. The salt-mediated stress-alleviating activity of CSW was studied by growing the green gram stems in different concentration of sodium chloride, that is, 25, 50, and 75 mM along with 0.1% of CSW and control experiment was run in parallel to compare the results. It was observed that CSW at 0.1% mitigated the salt stress up to a 50 mM concentration level and promoted the normal root growth and increased the plant biomass by 18.86% over the control (<i>p</i> = .01). The entire assay work, except pot trial, was completed in 21 days, hence it could a useful test method to assess the biostimulant and or salt mediated stress alleviating activities of biostimulants.