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.

将海藻提取物施用于作物后，已被证实可带来多项益处：提升作物产量与品质、增强作物对生物与非生物胁迫的抗性，并提高养分利用效率。本研究以红藻（<i>Gracilaria salicornia</i>）与褐藻（<i>Sargassum swartzii</i>）提取物复配制备了浓缩海藻提取物（concentrated seaweed extract, CSW），并采用绿豆（<i>Vigna radiata</i>）幼苗法评估其生物刺激活性与盐胁迫缓解活性。经检测，该CSW的可溶性固形物含量为29.93±0.84%，且含有大量元素、中微量元素、植物生长调节剂（生长素、细胞分裂素与赤霉素）、氨基酸及褐藻酸。通过将绿豆幼苗茎段扦插于不同浓度的CSW中培养10天，采用WinRhizo Pro根系成像系统对生成的根系进行量化分析，以此评估CSW的生物刺激活性。为评估CSW的盐胁迫缓解活性，本研究设置不同浓度的氯化钠胁迫体系（25、50、75 mM），并分别添加0.1%的CSW，同时设置平行对照组以比对实验结果。实验结果显示，0.1%浓度的CSW可在50 mM氯化钠胁迫下有效缓解盐害，促进根系正常生长，且相较于对照组，植株生物量提升18.86%（p=0.01）。本实验除盆栽试验外，全部流程耗时21天，因此该方法可作为评估生物刺激素生物刺激活性与盐胁迫缓解活性的有效检测手段。